[TASK] Use noncapturing expression for vendor|typo3_src in _.htaccess

Resolves: #76352
Releases: master, 7.6
Change-Id: I8332c93f1171d030d4198091779c8f1242c9337b
Reviewed-on: https://review.typo3.org/48360


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>