Use Mock in MockedFunction

This change allows `MockedFunction` to be used where `Mock` can be used. I don't think this fundamentally changes `MockedFunction`, just makes it more robust. This would resolve issues where an extended expect method takes a `Mock` type, but the mocking library uses `MockedFunction`.

Related issues:
extend-chrome/jest-chrome#9
jest-community/jest-extended#292

types/jest/index.d.ts

@@ -1107,7 +1107,7 @@ declare namespace jest {
      *  const mockMyFunction = myFunction as jest.MockedFunction<typeof myFunction>;
      *  expect(mockMyFunction.mock.calls[0][0]).toBe(42);
      */
-    type MockedFunction<T extends (...args: any[]) => any> = MockInstance<ReturnType<T>, ArgsType<T>> & T;
+    type MockedFunction<T extends (...args: any[]) => any> = Mock<ReturnType<T>, ArgsType<T>> & T;
 
     /**
      * Wrap a class with mock definitions