[BUGFIX] PHP 7.1: Non-numeric value encountered

$foo = 1 + 'aString'; in PHP 7.1 throws:
PHP Warning: A non-numeric value encountered in ...

Fix this by removing a test that tests this language
construct only instead of the test subject.

Change-Id: I74117cfd003bb525b0a7a674df4aae45d8f92299
Resolves: #76948
Releases: master, 7.6
Reviewed-on: https://review.typo3.org/48813


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Steffen Müller <typo3@t3node.com>
Tested-by: Steffen Müller <typo3@t3node.com>