test(upgrade): update test failure cause descriptions (#27660)

The changes here clarify that we now have a better description
of the root cause of the failure.

PR Close #27660

packages/upgrade/test/static/integration/downgrade_component_spec.ts

@@ -22,7 +22,7 @@ withEachNg1Version(() => {
     beforeEach(() => destroyPlatform());
     afterEach(() => destroyPlatform());
 
-    fixmeIvy('FW-716: Error: [$rootScope:inprog] $digest already in progress')
+    fixmeIvy('FW-715: ngOnChanges being called a second time unexpectedly')
         .it('should bind properties, events', async(() => {
               const ng1Module = angular.module('ng1', []).run(($rootScope: angular.IScope) => {
                 $rootScope['name'] = 'world';

packages/upgrade/test/static/integration/upgrade_component_spec.ts

@@ -3336,7 +3336,8 @@ withEachNg1Version(() => {
          }));
 
 
-      fixmeIvy('FW-713: ngDestroy not being called when downgraded ng2 component is destroyed')
+      fixmeIvy(
+          'FW-843: destroy hooks are not registered on upgraded ng1 components contained in ng2 component templates under ivy')
           .it('should call `$onDestroy()` on controller', async(() => {
                 const controllerOnDestroyA = jasmine.createSpy('controllerOnDestroyA');
                 const controllerOnDestroyB = jasmine.createSpy('controllerOnDestroyB');