Reserve refs/replace cos `git-replace` is using it

See:
* https://www.kernel.org/pub/software/scm/git/docs/git-replace.html
* https://git-scm.com/book/en/v2/Git-Tools-Replace

app/models/repository.rb

@@ -8,6 +8,7 @@ class Repository
   RESERVED_REFS_NAMES = %W[
     heads
     tags
+    replace
     #{REF_ENVIRONMENTS}
     #{REF_KEEP_AROUND}
     #{REF_ENVIRONMENTS}

changelogs/unreleased/38234-reserve-refs-replace.yml

+---
+title: Also reserve refs/replace after importing a project
+merge_request: 14436
+author:
+type: fixed