Customize: Remove the deprecated `-precomposed` suffix from `apple-touch-icon`...

Customize: Remove the deprecated `-precomposed` suffix from `apple-touch-icon` link in `wp_site_icon()`.

Props mukto90, khag7.
Fixes #48555.
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git-svn-id: https://core.svn.wordpress.org/trunk@46498 1a063a9b-81f0-0310-95a4-ce76da25c4cd