Fix $watch docs to correctly define when angular.equals is used

[myitcv]

Per my question in the Google Group

This is a first cut - I will rebase and fix the commit message when we're happy this is good to go.

[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 (#7633)

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!

[rodyhaddad]

landed as 11170ae

I changed your <a href...> to use markdown links