Update actions/upload-artifact action to v7

Author: renovate[bot]

.github/workflows/gradle.yml

@@ -27,7 +27,7 @@ jobs:
         id: get_version
         run: VERSION=$(./gradlew currentVersion -q -Prelease.quiet) && echo "VERSION=$VERSION" >> $GITHUB_OUTPUT
       - name: Upload sshj-plugin jar
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           # Artifact name
           name: Grails-Plugin-${{ steps.get_version.outputs.VERSION }}