Fixes link to custom test runner (#137)

Author: Syhids

index.md

@@ -65,7 +65,7 @@ The plugin also sets up compile dependencies for your tests, so you can now just
 
 Take a look at our [example build.gradle](https://github.com/facebook/screenshot-tests-for-android/blob/master/examples/app-example/build.gradle).
 
-NOTE: By default this overrides your instrumentation test runner, and depending on your set up this can cause problems. See [Custom InstrumentationTestRunners](#custom-instrumentation-test-runners) for how to avoid this.
+NOTE: By default this overrides your instrumentation test runner, and depending on your set up this can cause problems. See [Custom Test Runner](#custom-test-runner) for how to avoid this.
 
 **Layout Hierarchy Plugins**