Fix typos (#7050)

Uses https://en.wikipedia.org/wiki/Wikipedia:Lists_of_common_misspellings/For_machines to find likely typos, with https://github.com/bwignall/typochecker to help automate the checking.
diff --git a/python/mox.py b/python/mox.py
index 43db021..9dd8ac7 100755
--- a/python/mox.py
+++ b/python/mox.py
@@ -705,7 +705,7 @@
     """Move this method into group of calls which may be called multiple times.
 
     A group of repeating calls must be defined together, and must be executed in
-    full before the next expected mehtod can be called.
+    full before the next expected method can be called.
 
     Args:
       group_name: the name of the unordered group.