Bug 1595105 - Fix browser_webconsole_context_menu_copy_message_with_async_stacktrace.js perma failure on beta simulation. r=aryx.

Let's set javascript.options.asyncstack in the test to
have the async stacktrace displayed.

Differential Revision: https://phabricator.services.mozilla.com/D52697

--HG--
extra : moz-landing-system : lando

devtools/client/webconsole/test/browser/browser_webconsole_context_menu_copy_message_with_async_stacktrace.js

@@ -35,6 +35,7 @@ httpServer.registerPathHandler("/test.js", function(_, response) {
 const TEST_URI = `http://localhost:${httpServer.identity.primaryPort}/`;
 
 add_task(async function() {
+  await pushPref("javascript.options.asyncstack", true);
   const hud = await openNewTabAndConsole(TEST_URI);
 
   info("Call the log function defined in the test page");