Revert "Enable webapp support"

This reverts commit 0cb1ddfa50.

While technically working, the iOS webapp switches back to the browser
whenever the page URL changes.

lib/music_library_web/components/layouts/root.html.heex

@@ -4,7 +4,6 @@
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />
     <meta name="csrf-token" content={get_csrf_token()} />
-    <meta name="apple-mobile-web-app-capable" content="yes" />
     <.live_title suffix=" · Music Library">
       {assigns[:page_title] || assigns.conn.request_path}
     </.live_title>