Fix bower import paths in tests

Update paths to the same pattern as used in all elements
(i.e. use same relative paths to folder 'bower_components').

Change-Id: I0f5c2343c4037021e4f861a3ebad3cd71a249965
diff --git a/polygerrit-ui/app/test/gr-diff-comment-test.html b/polygerrit-ui/app/test/gr-diff-comment-test.html
index 9c7796c..9d06c3f 100644
--- a/polygerrit-ui/app/test/gr-diff-comment-test.html
+++ b/polygerrit-ui/app/test/gr-diff-comment-test.html
@@ -18,12 +18,12 @@
 <meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
 <title>gr-diff-comment</title>
 
-<script src="../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
-<script src="../../bower_components/web-component-tester/browser.js"></script>
-<script src="../../bower_components/page/page.js"></script>
+<script src="../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
+<script src="../bower_components/web-component-tester/browser.js"></script>
+<script src="../bower_components/page/page.js"></script>
 <script src="../scripts/util.js"></script>
 
-<link rel="import" href="../../bower_components/iron-test-helpers/iron-test-helpers.html">
+<link rel="import" href="../bower_components/iron-test-helpers/iron-test-helpers.html">
 <link rel="import" href="../elements/gr-diff-comment.html">
 
 <test-fixture id="basic">