ci: run on tag, skip firefox build

Author: dumbmoron

.github/workflows/main.yml

@@ -1,8 +1,9 @@
 name: uBO release
 
 on:
-  create:
-    branches: master
+  push:
+    tags:
+      - '*'
 
 permissions:
   contents: read
@@ -28,7 +29,6 @@ jobs:
       - name: Build MV2 packages
         run: |
           tools/make-chromium.sh ${{ env.VERSION }}
-          tools/make-firefox.sh ${{ env.VERSION }}
       - name: Assemble release notes
         run: |
           > release.body.txt
@@ -47,4 +47,3 @@ jobs:
           body_path: release.body.txt
           files: |
             dist/build/uBlock0_${{ env.VERSION }}.chromium.zip
-            dist/build/uBlock0_${{ env.VERSION }}.firefox.xpi