Remove special handling of view-mode from CustomElementsNormalizer

@fago this feels logical to me, but I'm running this by you for review, because I'm not the original author.

Especially the extra removal of "is" that I'd like to do.

Also: this is more related to 🐛 drupal prefix is added to configured custom element names Active :

I just saw that the removal of 'type' and 'view-mode' attributes needs a Change Record. Since this is an incompatibility from v2 that people may want to fix quickly while doing the update from v2, I added a code example.

I am assuming you did not want to add these setAttribute() calls back in the 'auto processing' case in CustomElementGenerator::buildEntityContent().

perfect, thank you!

>I feel like the 'is' handling right above here can also be removed.

I agree, this seems deprecated and is something we can drop as well!

Great. Since there's zero extra review or discussion to be done, I am just pushing the removal of the "is" attribute as part of this issue.

Without changing issue title. There is a separate change record for it now.

Automatically closed - issue fixed for 2 weeks with no activity.