[Network] az network application-gateway waf-policy managed-rule rule-set update: Allow updating rule group without rule IDs

src/azure-cli/azure/cli/command_modules/network/_validators.py

@@ -972,7 +972,5 @@ def process_appgw_waf_policy_update(cmd, namespace):    # pylint: disable=unused
     rule_group_name = namespace.rule_group_name
     rules = namespace.rules
 
-    if rules is None and rule_group_name is not None:
-        raise CLIError('--rules and --rule-group-name must be provided at the same time')
     if rules is not None and rule_group_name is None:
-        raise CLIError('--rules and --rule-group-name must be provided at the same time')
+        raise CLIError('--group-name must be provided when --rule is specified')

src/azure-cli/azure/cli/command_modules/network/custom.py

@@ -2096,7 +2096,7 @@ def update_waf_managed_rule_set(cmd, resource_group_name, policy_name,
     rule_group_override = {
         "rule_group_name": rule_group_name,
         "rules": managed_rule_overrides
-    } if managed_rule_overrides else None
+    } if rule_group_name is not None else None
 
     if rule_group_override is None:
         rule_group_overrides = []