Revert "Fixes #22310: Restore tracked placeholder in project-static/docs to prevent staticfiles warning (#22337)"

This reverts commit a72ab9007eb50d6f1d8b60e7668e84125d697141 to fix the pre-commit workflow.

.gitignore

@@ -14,10 +14,8 @@ yarn-error.log*
 # AI tooling
 .claude/settings.local.json
 
-# Documentation generated by the upgrade/build workflow.
-# Keep the placeholder so the directory exists in a fresh checkout.
-/netbox/project-static/docs/*
-!/netbox/project-static/docs/.gitkeep
+# Documentation generated by the upgrade/build workflow
+/netbox/project-static/docs/
 
 # Static files collected by Django
 /netbox/static/