Forget using the buildx step, it's not needed

.gitea/workflows/harmony_composer.yaml

@@ -1,5 +1,6 @@
 name: Compile and package harmony_composer
 on:
+  pull_request:
   push:
     branches:
       - master
@@ -26,8 +27,6 @@ jobs:
             target/x86_64-unknown-linux-gnu/release/harmony_composer
             target/x86_64-pc-windows-gnu/release/harmony_composer.exe
 
-      # TODO: build ARM images and MacOS binaries (or other targets) too
-
       - name: Setup log into hub.nationtech.io
         uses: docker/login-action@v3
         with:
@@ -35,8 +34,7 @@ jobs:
           username: ${{ secrets.HUB_BOT_USER }}
           password: ${{ secrets.HUB_BOT_PASSWORD }}
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+      # TODO: build ARM images and MacOS binaries (or other targets) too
 
       - name: Build and push
         uses: docker/build-push-action@v6