Bug 1651261 - Disable browser_ext_url_overrides_newtab.js on linux64. r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D84049

browser/components/extensions/test/browser/browser.ini

@@ -276,6 +276,7 @@ skip-if = os == 'mac' # Save as PDF not supported on Mac OS X
 [browser_ext_themes_validation.js]
 [browser_ext_topSites.js]
 [browser_ext_url_overrides_newtab.js]
+skip-if = os == 'linux' && os_version == '18.04' && bits == 64 # Bug 1651261
 [browser_ext_urlbar.js]
 [browser_ext_user_events.js]
 [browser_ext_webRequest.js]