Fixing a comment (#398)

Author: jrinehart-buf

proto/protovalidate/buf/validate/validate.proto

@@ -274,7 +274,7 @@ message FieldRules {
   // message UpdateRequest {
   //   // The uri rule only applies if the field is not an empty string.
   //   string url = 1 [
-  //     (buf.validate.field).ignore = IGNORE_IF_UNPOPULATED,
+  //     (buf.validate.field).ignore = IGNORE_IF_ZERO_VALUE,
   //     (buf.validate.field).string.uri = true
   //   ];
   // }