fix link

Author: sarven

README.md

@@ -39,7 +39,7 @@ So in these examples, I will try to share some tips on what to do to write good
     * [Mocking concrete classes](#mocking-concrete-classes)
     * [Testing private methods](#testing-private-methods)
     * [Time as a volatile dependency](#time-as-a-volatile-dependency)
-18. [100% Test Coverage shouldn't be the goal](#100%-test-coverage-shouldn't-be-the-goal)
+18. [100% Test Coverage shouldn't be the goal](#100-test-coverage-shouldnt-be-the-goal)
 19. [Recommended books](#recommended-books)
 
 ## Introduction