update url_embed to 3.x instead of 2.x branch

Based on the suggestion here:

https://www.drupal.org/project/url_embed/issues/3465030#comment-15707313 💬 'url_prefix' is not a supported key. Closed: works as designed

url_embed should be updated to the 3.x branch. Simply replacing the url_embed module for testing leads to issues with social_embed.

Did not find a solution in a first run.