dirstate: fix some typos in docstrings

I was passing by and they've been bothering me. :)

Differential Revision: https://phab.mercurial-scm.org/D12443

mercurial/dirstatemap.py

@@ -85,16 +85,16 b' class _dirstatemapcommon:'
     # with minor difference between implementation.
 
     def _dirs_incr(self, filename, old_entry=None):
-        """incremente the dirstate counter if applicable
+        """increment the dirstate counter if applicable
 
-        This might be a no-op for some subclass who deal with directory
+        This might be a no-op for some subclasses who deal with directory
         tracking in a different way.
         """
 
     def _dirs_decr(self, filename, old_entry=None, remove_variant=False):
-        """decremente the dirstate counter if applicable
+        """decrement the dirstate counter if applicable
 
-        This might be a no-op for some subclass who deal with directory
+        This might be a no-op for some subclasses who deal with directory
         tracking in a different way.
         """