requireResolversForArgs incorrectly labelled as missing with subscription args

**Describe the bug**
When arguments are added to the subscription type on the graphQL schema the requireResolversForArgs is incorrectly erroring.

```graphql
type Subscription {
numberIncremented(id: Int): Int
}
```

`Resolver missing for "Subscription.numberIncremented".`

**To Reproduce**
Example forked from official Apollo-server example:
https://codesandbox.io/s/pensive-joliot-brxcj?file=/index.js

**Expected behavior**
If arguments taken off the subscription type in the schema, everything works fine.

- OS:
- `@graphql-tools/...`: 7.1.5

Start with the provided CodeSandbox reproduction, especially index.js, and trace the requireResolversForArgs validation for Subscription.numberIncremented when the field has an id argument. Confirm the failure against @graphql-tools version 7.1.5 and verify that the subscription schema no longer reports a missing resolver while the argument remains present.

Written by the indexing model from the issue text.