docs(tutorial/13 - REST and Custom Services): added ngRoute dependanc…

[peterneave]

Omitted the existing ngRoute dependency.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Docs update.

What is the current behavior? (You can also link to an open issue here)
The tutorial user would follow the documentation and find that routing no longer works for step 13.

What is the new behavior (if this is a feature change)?
The tutorial user would follow the documentation and find that routing still works for step 13.

Does this PR introduce a breaking change?
Should have no effect as it is documentation.

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:

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[peterneave]

I signed it!

[googlebot]

CLAs look good, thanks!

[googlebot]

CLAs look good, thanks!

[gkalpak]

Good catch! Thx 👍