Fix Learn More button href.

app/assets/javascripts/issuable_time_tracker.js.es6

@@ -145,7 +145,7 @@
                   <code>/spend</code>
                   will update the sum of the time spent.
                 </p>
-                <a class='btn btn-default learn-more-button' href='http://example.com/time-tracking-url'>Learn more</a>
+                <a class='btn btn-default learn-more-button' href='https://docs.gitlab.com/ee/workflow/time_tracking.html'>Learn more</a>
               </div>
             </div>
           </div>

spec/javascripts/issuable_time_tracker_spec.js.es6

@@ -166,7 +166,7 @@ function initComponent(time_estimate = 100000, time_spent = 5000 ) {
           });
 
           it('should link to the correct documentation', function(done) {
-            const correctUrl = 'http://example.com/time-tracking-url';
+            const correctUrl = 'https://docs.gitlab.com/ee/workflow/time_tracking.html';
 
             $(this.timeTracker.$el).find('.help-button').click();