Bug 1357486: Follow-up: Skip optional permissions test with e10s disabled.

MozReview-Commit-ID: CadIoyzBeJ6

browser/base/content/test/webextensions/browser.ini

@@ -24,6 +24,7 @@ support-files =
 [browser_permissions_local_file.js]
 [browser_permissions_mozAddonManager.js]
 [browser_permissions_optional.js]
+skip-if = !e10s
 [browser_permissions_unsigned.js]
 skip-if = require_signing
 [browser_update_checkForUpdates.js]