[12.x] Update forever cookie factory docblock to reflect 400-day duration

[jackbayliss]

Was poking some cookie bits and noticed this.

The concrete implementation uses a 400 day duration (to align with Chromes 400 day max-age I believe) but the interface docblock still references "five years." This PR just keeps the contract aligned 🤷🏻

framework/src/Illuminate/Cookie/CookieJar.php

Lines 73 to 86 in 8469f5e

	/**
	* Create a cookie that lasts "forever" (400 days).
	*
	* @param string $name
	* @param string $value
	* @param string|null $path
	* @param string|null $domain
	* @param bool|null $secure
	* @param bool $httpOnly
	* @param bool $raw
	* @param string|null $sameSite
	* @return \Symfony\Component\HttpFoundation\Cookie
	*/
	public function forever($name, $value, $path = null, $domain = null, $secure = null, $httpOnly = true, $raw = false, $sameSite = null)

Targeted 12 as it's boring docbloc bits..