[TASK] Improve wording in maintenance section of Install Tool

Use proper HTML markup to improve readability.

Resolves: #84912
Releases: master
Change-Id: I384b5b048ed39cf0ebae017e7a2f1dbb1b52bc49
Reviewed-on: https://review.typo3.org/56848


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>