Property 'enter' does not exist on type '{ readonly enter?: ASTVisitFn<NameNode> ...

**Describe the bug**

Getting the following build errors with TS:

```
node_modules/@graphql-codegen/plugin-helpers/oldVisit.d.ts:5:75 - error TS2339: Property 'enter' does not exist on type '{ readonly enter?: ASTVisitFn | undefined; readonly leave: ASTReducerFn; } | { readonly enter?: ASTVisitFn | undefined; readonly leave: ASTReducerFn<...>; } | ... 41 more ... | undefined'.

5 enter?: Partial>;
~~~~~~~

node_modules/@graphql-codegen/plugin-helpers/oldVisit.d.ts:6:75 - error TS2339: Property 'leave' does not exist on type '{ readonly enter?: ASTVisitFn | undefined; readonly leave: ASTReducerFn; } | { readonly enter?: ASTVisitFn | undefined; readonly leave: ASTReducerFn<...>; } | ... 41 more ... | undefined'.

6 leave?: Partial>;
```

**To Reproduce**

Use together:

```
"@graphql-codegen/plugin-helpers": "^2.4.1",
"graphql": "^16.3.0"
```

Then just importing it will trigger the bug:

```ts
import type { Types } from '@graphql-codegen/plugin-helpers';
```

1. My GraphQL schema:

```graphql
N/A
```

2. My GraphQL operations:

```graphql
N/A
```

3. My `codegen.yml` config file:

```yml
N/A
```

**Expected behavior**

Not produce build errors.

**Environment:**

- OS: macOS
- `@graphql-codegen/plugin-helpers`: 2.4.1
- NodeJS: v14.17.6

**Additional context**

N/A