build: Drop deprecated set-output commands, use latest version of softprops/action-gh-release explicitly

Signed-off-by: Felicitas Pojtinger <felicitas@pojtinger.com>

Author: pojntfx

.github/workflows/flatpak.yaml

@@ -52,10 +52,10 @@ jobs:
           path: /tmp/out
       - name: Extract branch name
         id: extract_branch
-        run: echo "##[set-output name=branch;]$(echo ${GITHUB_REF#refs/heads/})"
+        run: echo "branch=$(echo ${GITHUB_REF#refs/heads/})" >> $GITHUB_OUTPUT
       - name: Publish pre-release to GitHub releases
         if: ${{ github.ref == 'refs/heads/main' }}
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@v2.3.2
         with:
           tag_name: release-${{ steps.extract_branch.outputs.branch }}
           prerelease: true
@@ -64,7 +64,7 @@ jobs:
             /tmp/out/*/*
       - name: Publish release to GitHub releases
         if: startsWith(github.ref, 'refs/tags/v')
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@v2.3.2
         with:
           prerelease: false
           overwrite_files: true