message: docs: fix broken guide link (tutorial/index --> tutorial)
  Replace broken link (`tutorial/index`) with `tutorial`.
  PR Close
diff: After you understand the basic Angular building blocks, you can learn more
  about the features and tools that can help you develop and deliver Angular applications.
  -* Work through the [Tour of Heroes](tutorial/index) tutorial to get a feel for how to fit the basic building blocks together to create a well-designed application.
  +* Work through the [Tour of Heroes](tutorial) tutorial to get a feel for how to fit the basic building blocks together to create a well-designed application.
  * Check out the [Glossary](guide/glossary) to understand Angular-specific terms and usage.
  