Class Drupal\inline_entity_form\Element\InlineEntityForm extends deprecated class Drupal\Core\Render\Element\RenderElement.

Problem/Motivation

`InlineEntityForm` class in the Inline Entity Form module extends the deprecated `Drupal\Core\Render\Element\FormElement` class, which causes deprecation warnings when running Upgrade Status or preparing for Drupal 11:
`Class Drupal\inline_entity_form\Element\InlineEntityForm extends deprecated class Drupal\Core\Render\Element\RenderElement. Deprecated in drupal:10.3.0 and is removed from drupal:12.0.0. Use Drupal\Core\Render\Element\RenderElementBase instead.`

Steps to reproduce

1. Install Inline Entity Form module
2. Run Upgrade Status module scan
3. Review deprecation warnings for Inline Entity Form

Proposed resolution

Replace FormElement with FormElementBase in the element class:

• The use statement
• The class declaration
• The annotation

Remaining tasks

I am attaching a patch that can provide a workaround until this is fixed.