[TASK] Use silence operator `@` for test setup

PHP8.3 emits a warning for content handed over to
unserialize() which contains superflous content at
the end.

The silence operator `@` is now used to suppress
the test setup unserialize() to avoid this exact
warning as preparation for PHP8.3 introduction.

Can be verified before and after by executing:

> Build/Scripts/runTests.sh -p 8.3 -s unitDeprecated

Resolves: #101409
Releases: main, 12.4, 11.5
Change-Id: I5741cd86e8e0a8afedb49ad01676d0766d5fbfaa
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80070


Tested-by: Stefan B�rk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan B�rk <stefan@buerk.tech>