Fix mistakes in monkeypatch doc example

doc/monkeypatch.txt

@@ -24,14 +24,14 @@ patch this function before calling into a function which uses it::
 
     import os.path
     def getssh(): # pseudo application code
-        return os.path.join(os.expanduser("~admin"), '.ssh')
+        return os.path.join(os.path.expanduser("~admin"), '.ssh')
 
     def test_mytest(monkeypatch):
         def mockreturn(path):
             return '/abc'
         monkeypatch.setattr(os.path, 'expanduser', mockreturn)
         x = getssh()
-        assert x == '/abc'
+        assert x == '/abc/.ssh'
 
 After the test function finishes the ``os.path.expanduser`` modification
 will be undone.