fix typo

Author: smkhalsa

docs/custom-scalars.md

@@ -25,7 +25,7 @@ gql_build|schema_builder:
 The key in the yaml Map should be the name of our custom scalar in our schema (i.e. "Date"), and `name` should be the name of the Dart type.
 
 :::important
-We've included only the `schema_builder` above for brevity, but we will need to include this same type_overrides map for `data_builder`, `var_builder` `serializer_builder`, and `req_builder` as well. See the [complete build.yaml example](#complete-buildyaml-example) for more details.
+We've included only the `schema_builder` above for brevity, but we will need to include this same type_overrides map for `data_builder`, `var_builder`, `serializer_builder`, and `req_builder` as well. See the [complete build.yaml example](#complete-buildyaml-example) for more details.
 :::
 
 If our Dart type is not part of the `dart:core` library, we'd also need to import the file that contains the Dart type. DateTime _is_ a part of `dart:core`, but if it weren't, we'd import it like so: