chore(ci): always run validate-docs-links action (#53022)

We should unconditionally run this action so we can mark it as "required".

It only takes about 13 seconds for each PR so it shouldn't put too much additional load on our CI infra.

<img width="811" alt="image" src="https://github.com/vercel/next.js/assets/229881/5c8596e1-71be-4f09-ac29-e0c4a9f12253">

- Depends on the fix from #53021

.github/workflows/validate-docs-links.yml

@@ -1,9 +1,7 @@
 name: 'Validate Doc Links'
 on:
   pull_request:
-    paths:
-      - 'docs/**.mdx'
-      - 'errors/*.mdx'
+    types: [opened, synchronize]
 
 jobs:
   link-check: