Improve TypeScript example for conditional Omit usage

[huggingbot]

Description

This PR updates the TypeScript documentation with a clearer example of using Omit with conditional types. The new example makes it easier to understand how to conditionally remove properties based on the value of quantity.

Changes

• Replaced the previous singleItemPayload example with a more precise generic type SingleItemPayload<T>.
• Improved the explanation and updated the example to show how color is omitted when quantity === 1.

Before

const singleItemPayload = Omit<CartItem, "color" extends string ? "color" : never>;
const cartPayload: singleItemPayload[] = [];

After

type SingleItemPayload<T extends CartItem> = T extends { quantity: 1 }
  ? Omit<T, 'color'>
  : T

const cartPayload: SingleItemPayload<CartItem & { quantity: 1 }>[] = [
  { productId: 123, quantity: 1 },
];