Remove unneeded files from third_party/polymer.

third_party/polymer/v1_0/components-chromium/iron-test-helpers/README.md

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-
-# iron-test-helpers
-
-A set of utility classes to make testing easier. For more details on the methods
-available, please check the documentation of `mock-interactions.js` and
-`test-helpers.js`
-
-## Mock Interactions
-
-This is a set of methods to simulate mouse or keyboard interaction with an element. Include `mock-interactions.js` and then use them like so:
-
-```javascript
-test('can be triggered with space', function(done) {
-  button.addEventListener('keydown', function() {
-    done();
-  });
-  MockInteractions.pressSpace(button);
-});
-
-test('can be clicked', function(done) {
-  button.addEventListener('click', function() {
-    done();
-  });
-  MockInteractions.tap(button);
-});
-```