Prevent <em> wrap of <i lang="en">Example</i> with ckeditor5

Problem/Motivation

BEFORE

<i lang="en">Example</i>

becomes

<em><i lang="en">Example</i></em>

AFTER PATCHING:

<i lang="en">Example</i>

Steps to reproduce

See problem/motivation, ckeditor 5, Drupal 10 or Drupal 11.

Proposed resolution

See commit

Remaining tasks

Review

User interface changes

See problem/motivation

API changes

See commit.

Data model changes

See commit.