Add browser support alert in Jira Connect app

What does this MR do and why?

Related to #355539 (closed).

🚩 This is behind a feature flag jira_connect_oauth.

Adds an alert when the crypto web API is unavailable to the user. Any browser supported by GitLab supports the crypto API. The alert directs the user to GitLab's supported browsers.

The crypto API is only used when the jira_connect_oauth FF is enabled.

Screenshots or screen recordings

How to set up and validate locally

1. Set up Jira and Gitpod using the steps here: https://docs.gitlab.com/ee/development/integrations/jira_connect.html
2. Apply this diff (in Gitpod):

diff --git a/app/assets/javascripts/jira_connect/subscriptions/components/app.vue b/app/assets/javascripts/jira_connect/subscriptions/components/app.vue
index 9155a095e38..6b87bb9863c 100644
--- a/app/assets/javascripts/jira_connect/subscriptions/components/app.vue
+++ b/app/assets/javascripts/jira_connect/subscriptions/components/app.vue
@@ -55,10 +55,7 @@ export default {
      * Any web API that the GitLab for Jira app depends on should be checked here.
      */
     isBrowserSupported() {
-      return (
-        !this.glFeatures.jiraConnectOauth ||
-        (this.glFeatures.jiraConnectOauth && AccessorUtilities.canUseCrypto())
-      );
+      return false;
     },
   },
   created() {

1. Reload the Jira Connect app. The alert should be visible.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #355539 (closed)