workflows: Use flatpak-builder action master version

Since "flatpak-builder" action uses deprecated "upload-artifact"
version, that can stop working soon, disable it and upload ourselves.
This is supported in master, but not in any tagged version,
so for now switch to using action from master branch.

Also bump used runtime to GNOME 47 when building.

.github/workflows/flatpak.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 600
     container:
-      image: bilelmoussaoui/flatpak-github-actions:gnome-45
+      image: bilelmoussaoui/flatpak-github-actions:gnome-47
       options: --privileged
     strategy:
       matrix:
@@ -33,9 +33,16 @@ jobs:
       with:
         platforms: arm64
     - name: Build
-      uses: bilelmoussaoui/flatpak-github-actions/flatpak-builder@v6
+      uses: flatpak/flatpak-github-actions/flatpak-builder@master
       with:
         bundle: com.github.rafostar.Clapper.flatpak
         manifest-path: pkgs/flatpak/com.github.rafostar.Clapper.json
         cache-key: flatpak-builder-${{ github.sha }}
         arch: ${{ matrix.arch }}
+        upload-artifact: false
+    - name: Upload
+      uses: actions/upload-artifact@v4
+      with:
+        name: clapper-flatpak-${{ matrix.arch }}
+        path: com.github.rafostar.Clapper.flatpak
+        if-no-files-found: error