ci: bump actions/setup-java from 5.7.0 to 6.0.0

* ci: bump actions/setup-java from 5.7.0 to 6.0.0

Bumps [actions/setup-java](https://github.com/actions/setup-java) from 5.7.0 to 6.0.0.
- [Release notes](https://github.com/actions/setup-java/releases)
- [Commits](actions/setup-java@v5.7.0...v6)

---
updated-dependencies:
- dependency-name: actions/setup-java
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* ci: bump actions/setup-java to v6, install gpg in screenshot container

Supersedes #2972, which had the same bump but left CI red.

setup-java v6 verifies the JDK signature with gpg. The ScreenshotTests
container has no gpg, so both matrix legs failed. Install gnupg there.

* ci: add gpg install step for ScreenshotTests, drop stray path file

* ci: remove stray `path` file

A file literally named `path`, containing the text .github/workflows/main.yml,
was committed by mistake. Nothing references it; delete it.

* ci: delete stray path file

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Riccardo Balbo <riccardo0blb@gmail.com>

Author: 3 people

.github/workflows/android-screenshot.yml

@@ -20,7 +20,7 @@ jobs:
       - name: checkout
         uses: actions/checkout@v7.0.1
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'

.github/workflows/j3o-scan.yml

@@ -31,7 +31,7 @@ jobs:
         uses: actions/checkout@v7.0.1
 
       - name: Set up Java
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: temurin
           java-version: '25'

.github/workflows/main.yml

@@ -62,7 +62,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7.0.1
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'
@@ -89,7 +89,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7.0.1
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'
@@ -116,7 +116,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7.0.1
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'
@@ -143,8 +143,15 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@v7.0.1
+      # setup-java v6 verifies the Temurin archive signature with gpg, which the
+      # GitHub-hosted runners ship, but this container image does not. Install it
+      # before the Java setup, otherwise the action fails with "gpg: not found".
+      - name: Install gpg
+        run: |
+          apt-get update -qq
+          DEBIAN_FRONTEND=noninteractive apt-get install -y -qq gnupg
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'
@@ -294,7 +301,7 @@ jobs:
           fetch-depth: 1
 
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: 25
@@ -334,7 +341,7 @@ jobs:
           fetch-depth: 1
 
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: ${{ matrix.jdk }}
@@ -419,7 +426,7 @@ jobs:
 
       # Setup jdk 25 used for building Maven-style artifacts
       - name: Setup the java environment
-        uses: actions/setup-java@b6effb05e454b25005698d916606bdc6ffcbf961 # v5
+        uses: actions/setup-java@dd06d9cba3e5552c54d9f8ea23572deb30010f7c # v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'
@@ -471,7 +478,7 @@ jobs:
 
       # Setup jdk 25 used for building Sonatype artifacts
       - name: Setup the java environment
-        uses: actions/setup-java@v5.7.0
+        uses: actions/setup-java@v6.0.0
         with:
           distribution: 'temurin'
           java-version: '25'