fix(db-mongodb): ensure relationships are stored in ObjectID (#8932)

### What?
Since the join field, we do store relationship fields values in
`ObjectID`. This wasn't true if the field is nested to an array /
blocks.

### Why?
All relationship fields values should be stored in `ObjectID`.

### How?
Fixes arrays / blocks handling in the `traverseFields.ts` function.
Before it didn't run for them.

test/joins/int.spec.ts

@@ -643,7 +643,6 @@ describe('Joins Field', () => {
         }
       }`
 
-      expect(true).toBeTruthy()
       const response = await restClient
         .GRAPHQL_POST({ body: JSON.stringify({ query }) })
         .then((res) => res.json())