Update CookieAuthenticationOptions XML documentation to clarify ExpireTimeSpan usage (dotnet#64122)

* Initial plan

* Update ExpireTimeSpan XML documentation to clarify usage

Co-authored-by: MackinnonBuck <[email protected]>

* Simplify documentation for `ExpireTimeSpan` property

* Update XML docs

* Use CookieBuilder.Expiration instead of CookieOptions.Expires in XML documentation

Co-authored-by: MackinnonBuck <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: MackinnonBuck <[email protected]>
Co-authored-by: Mackinnon Buck <[email protected]>

Author: Copilot

src/Security/Authentication/Cookies/src/CookieAuthenticationOptions.cs

@@ -128,8 +128,7 @@ public CookieBuilder Cookie
     /// even if it is passed to the server after the browser should have purged it.
     /// </para>
     /// <para>
-    /// This is separate from the value of <see cref="CookieOptions.Expires"/>, which specifies
-    /// how long the browser will keep the cookie.
+    /// This property should be used instead of <see cref="CookieBuilder.Expiration"/>, which is ignored.
     /// </para>
     /// </summary>
     public TimeSpan ExpireTimeSpan { get; set; }