Breaking: #78477 - Remove method FlashMessage->getMessageAsMarkup()

See Issue #78477

Description

The method FlashMessage->getMessageAsMarkup() has been removed.

Impact

Using this method will stop working immediately.

Affected Installations

All installations using the mentioned method above.

Migration

Use the new FlashMessageRendererResolver::class, for example:

GeneralUtility::makeInstance(FlashMessageRendererResolver::class)->resolve()->render()