fix(ci): run CI on all PRs to anywhere

fixes stacked PRs no-checks bug where
main < a < b
a merges into main
b is retargeted to main

but b doesn't run checks since it's not considered a new pr to main

now b will simply already have passing ci :)

.github/workflows/ci.yml

@@ -12,7 +12,6 @@ name: CI
 
 on:
   pull_request:
-    branches: [main]
   push:
     branches: [main]
 

.github/workflows/docker-publish.yml

@@ -16,7 +16,6 @@ on:
   # reports a status (path-gated workflows leave checks "pending" forever
   # when no matching files change, which blocks merge).
   pull_request:
-    branches: [main]
 
   release:
     types: [published]