docs($interval): fix missing square brackets in example

[JoshSchreuder]

Request Type: docs

How to reproduce: Go to https://docs.angularjs.org/api/ng/service/$interval

View example - bindings not complete and buttons do not work

Component(s):

Impact: small

Complexity: small

This issue is related to:

Detailed Description:

The docs example was missing closing ] for dependency injections.

Other Comments:

[mary-poppins]

Thanks for the PR! Please check the items below to help us merge this faster. See the contributing docs for more information.

• Uses the issue template (#8228)

If you need to make changes to your pull request, you can update the commit with git commit --amend.
Then, update the pull request with git push -f.

Thanks again for your help!

[caitp]

thanks @JoshSchreuder, lgtm