Update ngroute externs to include function as a valid type for $routeProvider.Params#template

See https://docs.angularjs.org/api/ngRoute/provider/$routeProvider but note
that the docs incorrectly claim that the function will be called with
Array.<Object>. The [source] shows that it is called with route.params, which
is Object<string, string>.

[source]: https://github.com/angular/angular.js/blob/v1.6.x/src/ngRoute/route.js#L809

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=167916688

Author: tjblasi

contrib/externs/angular-1.6.js

@@ -2299,7 +2299,7 @@ angular.$routeProvider.Params.prototype.controller;
 /** @type {string|undefined} */
 angular.$routeProvider.Params.prototype.controllerAs;
 
-/** @type {string|undefined} */
+/** @type {string|function(!Object<string, string>): string|undefined} */
 angular.$routeProvider.Params.prototype.template;
 
 /** @type {string|!Object|function(!Object<string,string>=)} */