keyword: move repo.__class__ assignment out of monkeypatch context

A cosmetic change to improve readability.

hgext/keyword.py

@@ -636,8 +636,6 b' def reposetup(ui, repo):'
         finally:
             wlock.release()
 
-    repo.__class__ = kwrepo
-
     def kwfilectx_cmp(orig, self, fctx):
         # keyword affects data size, comparing wdir and filelog size does
         # not make sense
@@ -661,6 +659,8 b' def reposetup(ui, repo):'
         except KeyError:
             pass
 
+    repo.__class__ = kwrepo
+
 cmdtable = {
     'kwdemo':
         (demo,