repair: remove unnecessary locking for bookmarks

The caller has already locked the repo.

mercurial/repair.py

@@ -216,7 +216,6 b' def strip(ui, repo, nodelist, backup=Tru'
         for m in updatebm:
             bm[m] = repo[newbmtarget].node()
 
-        with repo.lock():
             with repo.transaction('repair') as tr:
                 bm.recordchange(tr)