Fix well known self check

roles/matrix-server/tasks/self_check/self_check_well_known.yml

@@ -2,7 +2,7 @@
 
 - set_fact:
     well_known_url_matrix: "https://{{ hostname_matrix }}/.well-known/matrix/client"
-    well_known_url_identity: "https://{{ hostname_matrix }}/.well-known/matrix/client"
+    well_known_url_identity: "https://{{ hostname_identity }}/.well-known/matrix/client"
 
 
 - name: Check .well-known on the matrix hostname