copies: return consistent type from revinfo

The return is expected to be a list, so we should return a list. This make the
use of this function from type-checked language (eg: rust) much simpler.

mercurial/copies.py

@@ -231,7 +231,7 b' def _revinfogetter(repo):'
             else:
                 p1copies = {}
                 p2copies = {}
-                removed = ()
+                removed = []
             return p1, p2, p1copies, p2copies, removed
 
     else: