refactor(GraphQL): Pointer constraint input type as ID (#6020)

* refactor(GraphQL): Pointer constraint input type as ID

Redefines the Pointer constraint input type from a custom scalar to
a simple ID.

* fix: PR review requested changes

src/GraphQL/loaders/parseClassQueries.js

@@ -120,7 +120,8 @@ const load = function(
             config,
             auth,
             info,
-            selectedFields.map(field => field.split('.', 1)[0])
+            selectedFields.map(field => field.split('.', 1)[0]),
+            parseClass.fields
           );
         } catch (e) {
           parseGraphQLSchema.handleError(e);