Repo: Incorporate void check into isNullableType?

[kirkwaiblinger]

Suggestion

In https://github.com/typescript-eslint/typescript-eslint/pull/8912/files#r1572612158, the void type is treated as a nullable type for the purposes of no-unnecessary-type-assertion, the same as null and undefined would be. Consider whether checking for the void type should be incorporated into the helper method isNullableType already used for checking for the null and undefined type, and assess whether its impact on other rules that use that helper is a correct behavior change or not.