teleport: Add explicit WebAuthn config, not just U2F.

WebAuthn is the default, replacing U2F, in Teleport 10 and above[1].
While Teleport can derive a WebAuthn configuration from a U2F
configuration[2], it's useful to be explicit.

[1]: https://goteleport.com/docs/access-controls/guides/webauthn/
[2]: https://goteleport.com/docs/access-controls/guides/webauthn/#u2f

puppet/zulip_ops/files/teleport_server.yaml

@@ -12,11 +12,8 @@ auth_service:
     second_factor: on
     u2f:
       app_id: https://teleport.zulipchat.net
-      facets:
-        - https://teleport.zulipchat.net:443
-        - https://teleport.zulipchat.net
-        - teleport.zulipchat.net:443
-        - teleport.zulipchat.net
+    webauthn:
+      rp_id: teleport.zulipchat.net
 
 proxy_service:
   enabled: "yes"