Docs: custom scalar example contains invalid types
### Issue Description

The typescript version of the custom scalar example has errors:
https://www.apollographql.com/docs/apollo-server/schema/custom-scalars/#example-the-date-scalar

### Link to Reproduction

JYWwDg9gTgLgBAbzgcSgQzACwIoBkDKAxmgDZpQAqAnmAKYA0cA0sAHYAmcAvnAGZQQQcAOQBzdFgCOJYQG4AsACglhCKwDO8dmhi0ipcnAC8cVrQDuKCTgLEylGrQAUCJXFNoQtAFwiAIjq0wvRucOy06oRQwGAwwGq

### Reproduction Steps

Paste the example in the typescript online playground (see reproduction link) and observe the errors