Bug 1742167 - Disable managedbookmarks test on Linux. r=mstriemer

Differential Revision: https://phabricator.services.mozilla.com/D138811

browser/components/enterprisepolicies/tests/browser/managedbookmarks/browser.ini

@@ -4,4 +4,5 @@ prefs =
 support-files =
   managedbookmarks.json
 
+skip-if = (os == "linux") # Popup timeout issue - see Bug 1742167
 [browser_policy_managedbookmarks.js]