actions: (Temporarily?) Switched default action to produce GTK3 versi…

…on, as GTK2 build unavailable at this moment.

.github/workflows/dockerimage.yml

@@ -15,7 +15,7 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Build the Docker image
-        run: docker build . --file Dockerfile --tag vasilev/palemoon
+        run: docker build . --file Dockerfile.gtk3 --tag vasilev/palemoon
 
       - name: Log into registries
         run: |