feat(client-mailmanager): Allow underscores in the local part of the input of the "Email recipients rewrite" action in rule sets.

Author: awstools

codegen/sdk-codegen/aws-models/mailmanager.json

@@ -2198,7 +2198,7 @@
           "min": 0,
           "max": 254
         },
-        "smithy.api#pattern": "^[0-9A-Za-z@+.-]+$",
+        "smithy.api#pattern": "^[a-zA-Z0-9._+-]+@[a-zA-Z0-9.-]+$",
         "smithy.api#sensitive": {}
       }
     },