build: disable flatpak caching

The workflow is not an official release build, hence nothing should be
cached. That was the reason why it was so slow, because it uploaded
stuff to the cache after the artifacts had been generated.

.github/workflows/build-flatpak.yml

@@ -34,7 +34,9 @@ jobs:
         with:
           bundle: io.github.bkueng.qMasterPassword
           manifest-path: ./data/flatpak/io.github.bkueng.qMasterPassword.yml
-          cache-key: flatpak-builder-${{ github.sha }}
+          # NOTE: this is not an official build hence nothing should be cached
+          cache: false
+          #cache-key: flatpak-builder-${{ github.sha }}
           upload-artifact: false
           verbose: true