Drop stale cron parenthetical from generate-docs.yml

update-docs.yml is workflow_dispatch only; the (cron + manual) note
contradicted the workflow definition and rules/ci.md.

Author: jeffhorn-nava

.github/workflows/generate-docs.yml

@@ -1,6 +1,6 @@
 name: Generate Strata Docs
 # Full regeneration is a deliberate, maintainer-run action — manual dispatch only.
-# Routine drift refresh + new-source pickup lives in update-docs.yml (cron + manual).
+# Routine drift refresh + new-source pickup lives in update-docs.yml.
 on:
   workflow_dispatch: