fix: made load_balancing_scheme a recommended field

Author: pawan1210

modules/backend/metadata.display.yaml

@@ -82,6 +82,7 @@ spec:
               value: EXTERNAL_MANAGED
             - label: INTERNAL_MANAGED
               value: INTERNAL_MANAGED
+          level: 1
         locality_lb_policy:
           name: locality_lb_policy
           title: Locality Lb Policy

modules/frontend/metadata.display.yaml

@@ -81,6 +81,7 @@ spec:
               value: EXTERNAL_MANAGED
             - label: INTERNAL_MANAGED
               value: INTERNAL_MANAGED
+          level: 1
         managed_ssl_certificate_domains:
           name: managed_ssl_certificate_domains
           title: Managed Ssl Certificate Domains