Docs: Update outdated Microsoft and Apple documentation links in WP_Site_Icon

[dilip2615]

Follow-up to #65940 / [63568].
After the Chrome documentation @link updates in WP_Site_Icon, two related @link URLs in the same file are still outdated:

1. Microsoft IE tile docs still use msdn.microsoft.com; should use the current Learn URL.
2. Apple icon docs still use a prerelease IconMatrix URL that redirects away; should use the current App Icons HIG page.

​https://github.com/WordPress/wordpress-develop/pull/13830

[mukesh27]

@sachinrajcp123 We already have a PR 13830 opened by the ticket author. Please don't open a duplicate PR or patch. Instead, review the existing PR and share your feedback there.

Description

Follow-up to r63568.

Updates remaining outdated @link URLs in WP_Site_Icon::$site_icon_sizes:

• Microsoft tile docs: msdn.microsoft.com -> current Learn URL
• Apple icon docs: prerelease IconMatrix URL -> current App Icons HIG

Trac ticket

https://core.trac.wordpress.org/ticket/66214

[SergeyBiryukov]

In 64029:

Docs: Update Microsoft and Apple documentation links for app icons in WP_Site_Icon.

Includes adding an up-to-date alternative for Chrome's “Add to Homescreen” link, previously removed in r63568.

Follow-up to r33202, r32994, r63568.

Props dilip2615, mukesh27, SergeyBiryukov.
Fixes #66214.