Remove on: create from CI

This doesn't appear to actually take a `tags` sub-argument, it's just
on-create of either a tag or a branch. This means that contributors
pushing to their own repositories with feature branches trigger builds,
but only on branch creation and not on further commits. This switches to
`on: push: tags` which should retain the behavior of running on tags.

.github/workflows/main.yml

@@ -1,9 +1,8 @@
 name: CI
 
 on:
-  create:
-    tags:
   push:
+    tags:
     branches:
       - main
       - faster-ci