`namingConvention` config is not applied when `enumsAsTypes: true`

### Describe the bug

I want to have an enum that is outputted as a Union type in kebab-case.

So that the following enum:
```gql
enum Options {
CHILD_SEAT
PET_CAGE_SMALL
PET_CAGE_LARGE
}
```

renders into:
```typescript
export type Options = 'child-seat' | 'pet-cage-small' | 'pet-cage-large'
```

But I wasn't able to find a way to achieve this. The `namingConvention` config seems to have no effect on union types.

### Your Example Website or App

https://codesandbox.io/s/serverless-microservice-fgh29z

### Steps to Reproduce the Bug or Issue

1. Have an enum with any values in the schema
2. Use `enumsAsTypes: true` alongside `namingConvention.enumValues: lodash#kebabCase`
3. Observe that generated union type uses the same case as defined in the GQL schema

### Expected behavior

As a user, I expect `namingConvention` to have an effect when used together with `enumsAsTypes: true`, but I see that it doesn't.

### Screenshots or Videos

_No response_

### Platform

- OS: macOS
- NodeJS: 16.16
- `graphql` version: 16.5.0
- `@graphql-codegen/cli` version: 2.9.1
- `@graphql-codegen/typescript` version: 2.7.2

### Codegen Config File

```yml
schema: schema.graphql
generates:
types.ts:
config:
enumsAsTypes: true
namingConvention:
enumValues: lodash#kebabCase
plugins:
- typescript
```

### Additional context

- It's impossible to have kebab-case in the GQL schema enum
- The types are to be used over existing DB, so it has to be snake case to avoid major refactoring