Bug 1343150 - Disable test_PreviewProvider.js on windows too; r=jmaher

browser/components/newtab/tests/browser/browser.ini

@@ -4,6 +4,6 @@ support-files =
   dummy_page.html
 
 [browser_PreviewProvider.js]
-skip-if = os == 'linux' # bug 1343150
+skip-if = os == 'linux' || os == 'win' # bug 1343150
 [browser_remotenewtab_pageloads.js]
 [browser_newtab_overrides.js]