Remove Flatpak Builder Workflow

.github/workflows/flatpak-builder.yml

@@ -1,19 +0,0 @@
-on:
-  push:
-    branches: [main]
-  pull_request:
-name: Flatpak Builder
-jobs:
-  build:
-    name: "Flatpak"
-    runs-on: ubuntu-latest
-    container:
-      image: bilelmoussaoui/flatpak-github-actions:gnome-47
-      options: --privileged
-    steps:
-    - uses: actions/checkout@v4
-    - uses: flatpak/flatpak-github-actions/flatpak-builder@v6.1
-      with:
-        bundle: io.github.flattool.Warehouse.flatpak
-        manifest-path: build-aux/io.github.flattool.Warehouse.json
-        cache-key: flatpak-builder-${{ github.sha }}