Fix typo in GoogleMock Cookbook.

PiperOrigin-RevId: 413674665
Change-Id: I466f87348390f42434a70f183efdf0557be9dddd

docs/gmock_cook_book.md

@@ -1084,7 +1084,7 @@ using ::testing::Lt;
 ```
 
 says that `Blah` will be called with arguments `x`, `y`, and `z` where `x < y <
-z`. Note that in this example, it wasn't necessary specify the positional
+z`. Note that in this example, it wasn't necessary to specify the positional
 matchers.
 
 As a convenience and example, gMock provides some matchers for 2-tuples,