upgrade: drop the prefix to the '_finishdatamigration' function

Now that we are in the 'upgrade' module we can simplify the name.

mercurial/upgrade.py

@@ -487,7 +487,7 b' def _filterstorefile(srcrepo, dstrepo, r'
 
     return True
 
-def _upgradefinishdatamigration(ui, srcrepo, dstrepo, requirements):
+def _finishdatamigration(ui, srcrepo, dstrepo, requirements):
     """Hook point for extensions to perform additional actions during upgrade.
 
     This function is called after revlogs and store files have been copied but
@@ -534,7 +534,7 b' def _upgraderepo(ui, srcrepo, dstrepo, r'
         dst = dstrepo.store.vfs.join(p)
         util.copyfile(src, dst, copystat=True)
 
-    _upgradefinishdatamigration(ui, srcrepo, dstrepo, requirements)
+    _finishdatamigration(ui, srcrepo, dstrepo, requirements)
 
     ui.write(_('data fully migrated to temporary repository\n'))