Adjust Omit's 2nd param to allow autocompletion of 1st param's keys

[EvanLovely]

Consider this code example when using Omit:

type Person = { 
  firstName: string; 
  lastName: string;
}
type X = Omit<Person, 'lastName'>;

Before, no autocompletion would happen when typing out 'lastName' and after this PR it does autocomplete the keys from Person.

Have a nice day! 👋

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[tjjfvi]

This is a breaking change; Omit<{ foo: 1 }, "bar"> being valid and a no-op is likely highly relied on

[AviVahl]

See discussion at #30825

[EvanLovely]

Makes sense; thanks for insight 👍