$assetManager->addJs( "https://cdn.ampproject.org/v0.js");

Use the "update-ping" mechanism to permanently remove content from the Google AMP Cache after the content has been removed from its origin. For example, to purge content formerly served at https://cdn.ampproject.org/i/s/example.com/favicon.ico, send an update ping request to:
https://cdn.ampproject.org/update-ping/i/s/example.com/favicon.ico.
Cached content that no longer exists will eventually get removed from the cache; it's just faster to use "update-ping".
Google's Remove AMP content "documentation"