tests(ngMock): remove a broken jqLite cache clearing (angular#16515)

This commit removes the resetting of `angular.element.cache` in some tests;
this was desynchronizing jqLite.cache & the local jqCache variable and since
some parts of the code use one of them and some the other one, it was breaking
JQLite._data. `angular.element.cache` doesn't even exist when jQuery 2+ is used.

Closes angular#16515
Refs angular#16512

Author: mgol

Diff for: test/ngMock/angular-mocksSpec.js

@@ -3123,10 +3123,6 @@ describe('sharedInjector', function() {
         define();
         sdescribe.root.run();
       } finally {
-        // avoid failing testability for the additional
-        // injectors etc created
-        angular.element.cache = {};
-
         // clear up
         module.$$beforeAllHook = null;
         module.$$afterAllHook = null;