Bump notifications-ruby-client from 5.4.0 to 6.2.0

Bumps [notifications-ruby-client](https://github.com/alphagov/notifications-ruby-client) from 5.4.0 to 6.2.0.
- [Changelog](https://github.com/alphagov/notifications-ruby-client/blob/main/CHANGELOG.md)
- [Commits](alphagov/notifications-ruby-client@5.4.0...6.2.0)

---
updated-dependencies:
- dependency-name: notifications-ruby-client
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -429,12 +429,12 @@ GEM
       net-imap
       net-pop
       net-smtp
-    mail-notify (1.2.0)
-      actionmailer (>= 5.2.4.6)
-      actionpack (>= 5.2.7.1)
-      actionview (>= 5.2.7.1)
-      activesupport (>= 5.2.4.6)
-      notifications-ruby-client (~> 5.1)
+    mail-notify (2.0.0)
+      actionmailer (>= 5.2.8.1)
+      actionpack (>= 5.2.8.1)
+      actionview (>= 5.2.8.1)
+      activesupport (>= 5.2.8.1)
+      notifications-ruby-client (~> 6.0)
       rack (>= 2.1.4.1)
     marcel (1.0.4)
     matrix (0.4.2)
@@ -467,7 +467,7 @@ GEM
     notiffany (0.1.3)
       nenv (~> 0.1)
       shellany (~> 0.0)
-    notifications-ruby-client (5.4.0)
+    notifications-ruby-client (6.2.0)
       jwt (>= 1.5, < 3)
     oj (3.16.6)
       bigdecimal (>= 3.0)