docs(ngMock): $log.error property contains messages from $log.error, not $log.log

Closes #5932

src/ngMock/angular-mocks.js

@@ -379,7 +379,7 @@ angular.mock.$LogProvider = function() {
        *
        * @example
        * <pre>
-       * $log.log('Some Error');
+       * $log.error('Some Error');
        * var first = $log.error.logs.unshift();
        * </pre>
        */