Fix schema error

Author: MarcialRosales

deps/rabbitmq_auth_backend_oauth2/priv/schema/rabbitmq_auth_backend_oauth2.schema

@@ -223,7 +223,7 @@
 {mapping,
  "auth_oauth2.proxy",
  "rabbitmq_auth_backend_oauth2.key_config.proxy",
- [{datatype, string}]}.
+ [{datatype, string}, {validators, ["uri"]}]}.
 
 {mapping,
  "auth_oauth2.proxy_username",
@@ -340,7 +340,7 @@
 {mapping,
  "auth_oauth2.oauth_providers.$name.proxy",
  "rabbitmq_auth_backend_oauth2.oauth_providers",
- [{datatype, string}]}.
+ [{datatype, string}, {validators, ["uri"]}]}.
 
 {mapping,
  "auth_oauth2.oauth_providers.$name.proxy_username",