[!!!][TASK] Remove global variable PARSETIME_START

The global variable $GLOBALS['PARSETIME_START'] is removed,
as it has been superseded by $GLOBALS['TYPO3_MISC']['microtime_start']
for a long time already.

Resolves: #82893
Releases: master
Change-Id: Ic738ebb1ae4dd19aff426fcd32b8f7a3594ca2e4
Reviewed-on: https://review.typo3.org/54517


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