fix(rootScope.js): edit $watch parameter comment

[dbwhddn10]

i think $watch listener params comment is wrong ( string value is not correct)

i think $watch listener params is same as $watchgroup listener and only function value

https://github.com/angular/angular.js/blob/master/src/ng/rootScope.js#L349-351

[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 (#8322)

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!

[cmmartin]

You can pass a string (an angular expression) to be executed as a $watch listener.

For example...
$scope.$watch('count1', 'count2 = count1');

http://jsfiddle.net/HB7LU/5156/

[caitp]

@cmmartin #8190

[cmmartin]

thanks :)

[petebacondarwin]

@dbwhddn10 - thanks for this. The description is not quite accurate but I have modified it and merged.