Fix email disclosure in user edit page title (GHSA-4cwq-j7jv-qmwg)

Security fix for IDOR-style information disclosure where the admin
email address was leaked in the <title> tag even on 403 Forbidden
responses.

The edit view title template previously included the email:
  {{ fullname ?? username }} <{{ email }}>

Now shows only the name/username without email:
  {{ fullname ?? username }}

This prevents low-privilege users from enumerating admin email
addresses by accessing /admin/accounts/users/{username} URLs.

system/blueprints/flex/user-accounts.yaml

@@ -72,7 +72,7 @@ config:
     # Edit view
     edit:
       title:
-        template: "{{ form.value('fullname') ?? form.value('username') }} <{{ form.value('email') }}>"
+        template: "{{ form.value('fullname') ?? form.value('username') }}"
 
     # Configure view
     configure: