Merge pull request #1212 from TheKhanj/docs/add-missing-comma

docs: Add missing comma

docs/reference/creating_test_doubles.rst

@@ -419,7 +419,7 @@ additional modifier:
     \Mockery::mock('MyClass')->shouldIgnoreMissing()->asUndefined();
 
 The returned object is nothing more than a placeholder so if, by some act of
-fate, it's erroneously used somewhere it shouldn't it will likely not pass a
+fate, it's erroneously used somewhere it shouldn't, it will likely not pass a
 logic check.
 
 We have encountered the ``makePartial()`` method before, as it is the method we