Fixing ghactions to trigger on build of main

.github/workflows/build_main.yml

@@ -1,5 +1,5 @@
 name: Build Main
-push:
+on push:
   branches:
     - main
 jobs:
@@ -20,5 +20,4 @@ jobs:
       - uses: actions/upload-artifact@v2
         with:
           name: Extension-XPI
-          path: web-ext-artifacts/firefox_translations-*.zip
-
+          path: web-ext-artifacts/firefox_translations-*.zip