Update git rerere link in docs

The original link was moved.

changelogs/unreleased/git-rerere-link-doc-update.yml

+---
+title: Update git rerere link in docs
+merge_request: 21060
+author: gfyoung
+type: other

doc/development/automatic_ce_ee_merge.md

@@ -100,7 +100,7 @@ Notes:
   number of times you have to resolve conflicts.
 - Please remember to
   [always have your EE merge request merged before the CE version](#always-merge-ee-merge-requests-before-their-ce-counterparts).
-- You can use [`git rerere`](https://git-scm.com/blog/2010/03/08/rerere.html)
+- You can use [`git rerere`](https://git-scm.com/docs/git-rerere)
   to avoid resolving the same conflicts multiple times.
 ### Cherry-picking from CE to EE