Replace the avatar stack in the header with an icon

This is a design update.

public/locales/en-GB/app.json

@@ -5,7 +5,6 @@
   "{{count}} stars|other": "{{count}} stars",
   "{{displayName}} is presenting": "{{displayName}} is presenting",
   "{{displayName}}, your call has ended.": "{{displayName}}, your call has ended.",
-  "{{names, list(style: short;)}}": "{{names, list(style: short;)}}",
   "<0></0><1></1>You may withdraw consent by unchecking this box. If you are currently in a call, this setting will take effect at the end of the call.": "<0></0><1></1>You may withdraw consent by unchecking this box. If you are currently in a call, this setting will take effect at the end of the call.",
   "<0>Already have an account?</0><1><0>Log in</0> Or <2>Access as a guest</2></1>": "<0>Already have an account?</0><1><0>Log in</0> Or <2>Access as a guest</2></1>",
   "<0>Create an account</0> Or <2>Access as a guest</2>": "<0>Create an account</0> Or <2>Access as a guest</2>",
@@ -74,6 +73,7 @@
   "Not now, return to home screen": "Not now, return to home screen",
   "Not registered yet? <2>Create an account</2>": "Not registered yet? <2>Create an account</2>",
   "Open in the app": "Open in the app",
+  "Participants": "Participants",
   "Password": "Password",
   "Passwords must match": "Passwords must match",
   "Profile": "Profile",