Revert "CI: enable spell check on git push"

This reverts commit 413aa6e2e94a591d444ef9bd174a99b64eea8436.

It reports failures that neither the patch's author nor the committer
are able to check for before pushing, causing an excess of failure
reports that can hardly be acted upon. We need to find a better
solution, let's revert it for now.

.github/workflows/codespell.yml

@@ -1,7 +1,8 @@
 name: Spelling Check
 
 on:
-  push:
+  schedule:
+    - cron: "0 0 * * 2"
 
 permissions:
   contents: read