Update merge.yml

Author: danirabbit

.github/workflows/merge.yml

@@ -37,7 +37,7 @@ jobs:
           flatpak install -y --arch=${{matrix.arch}} org.freedesktop.Sdk.Extension.rust-stable//23.08
 
       - name: Build
-        uses: flatpak/flatpak-github-actions/flatpak-builder@v6
+        uses: flatpak/flatpak-github-actions/flatpak-builder@v6.4
         with:
           bundle: videos.flatpak
           manifest-path: io.elementary.videos.yml