extensions: improve language for wrapfunction() docstring.

mercurial/extensions.py

@@ -138,8 +138,8 b' def wrapcommand(table, command, wrapper)'
 def wrapfunction(container, funcname, wrapper):
     '''Wrap the function named funcname in container
 
-    It is replacing with your wrapper. The container is typically a
-    module, class, or instance.
+    Replace the funcname member in the given container with the specified
+    wrapper. The container is typically a module, class, or instance.
 
     The wrapper will be called like