Bug 1763197 - Disable test_ext_userScripts_register.js without Fission. r=rpl

This test seems to fail frequently on Linux without Fission, and on Android,
when the parent controlled navigation pref is enabled, so disable the test
there. We don't really support non-Fission builds anyways, and apparently
containers aren't supported on Android.

Differential Revision: https://phabricator.services.mozilla.com/D154288

toolkit/components/extensions/test/xpcshell/xpcshell-common.ini

@@ -274,6 +274,9 @@ run-sequentially = very high failure rate in parallel
 [test_ext_userScripts_exports.js]
 run-sequentially = very high failure rate in parallel
 [test_ext_userScripts_register.js]
+skip-if =
+  os == "linux" && !fission # Bug 1763197
+  os == "android" # Bug 1763197
 [test_ext_wasm.js]
 [test_ext_webRequest_auth.js]
 skip-if = os == "android" && debug