Updated the Flatpak GitHub Actions workflow to fully disable Flatpak builder caching by setting cache: false and restore-cache: false in the flatpak-builder step (and removing the previous cache-key usage)

.github/workflows/flatpak-build.yml

@@ -31,7 +31,8 @@ jobs:
         with:
           bundle: zoitechat.flatpak
           manifest-path: flatpak/net.zoite.Zoitechat.json
-          cache-key: flatpak-builder-${{ github.sha }}
+          cache: false
+          restore-cache: false
 
       - name: Upload Flatpak Bundle
         id: upload_flatpak