[BUGFIX] Provide return value for SendEmailCommand

The parent class defines a return value of type int, but the command
does not provide one. This causes a test failure after latest dependency
update of codeception version 4.

Resolves: #90651
Releases: master
Change-Id: Iecb1f3aa95feee6a0276ad1a0660999523490a53
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63556


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Richard Haeser <richard@maxserv.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>