[BUGFIX] Use renderType selectSingle for field t3_tables of sys_action

The field t3_tables of sys_action must be rendered as a single
select field. This was also the behaviour before the regression
introduced with #69822.

Resolves: #81119
Releases: master, 8.7, 7.6
Change-Id: I2c885ea3494d7e2be22fad6df1b2a4791991551b
Reviewed-on: https://review.typo3.org/52691


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Thomas Hohn <thomas@hohn.dk>
Reviewed-by: Henrik Elsner <helsner@dfau.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>

typo3/sysext/sys_action/Configuration/TCA/sys_action.php

@@ -129,7 +129,7 @@ return [
             'label' => 'LLL:EXT:sys_action/Resources/Private/Language/locallang_tca.xlf:sys_action.t3_tables',
             'config' => [
                 'type' => 'select',
-                'renderType' => 'selectMultipleSideBySide',
+                'renderType' => 'selectSingle',
                 'special' => 'tables',
                 'items' => [
                     ['', '']