update linter ruleset

dev/tykapi-auth-ruleset.yaml

@@ -1,10 +1,14 @@
 extends: 'spectral:oas'
 
 rules:
-  check-for-jwt-auth:
-    description: APIs does not have JWT enabled
+  check-authentication-methods:
+    description: "At least one of 'enable_jwt' or 'use_mutual_tls_auth' must be true."
     given: "$.api_definition"
-    severity: error
     then:
-      field: 'enable_jwt'
-      function: falsy
+      - condition: "truthy"
+        field: "enable_jwt"
+        or:
+          - condition: "truthy"
+            field: "use_mutual_tls_auth"
+    severity: error
+    message: "At least one of 'api_definition.enable_jwt' or 'api_definition.use_mutual_tls_auth' must be true."