[FOLLOWUP][BUGFIX] Fix minor error handler code bugs

ErrorHandler should deal with the same severity for trigger_error()
for E_USER_DEPRECATED as GeneralUtility::deprecationLog()
when calling GeneralUtility::devLog().

Resolves: #82375
Releases: master, 8.7
Change-Id: Iaff5f96f5bd0a2d94bb3bc76d9d3fec2d019c901
Reviewed-on: https://review.typo3.org/54017


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>