[TASK] Document support of MySQL Strict mode

Document that the MySQL SQL modes STRICT_TRANS_TABLES and STRICT_ALL_TABLES
are supported. Remove the check for these SQL modes from the Install Tool.

Resolves: #72610
Releases: master, 7.6
Change-Id: I0b2500a7170bb18517560f87ee6a060c2d89b43e
Reviewed-on: https://review.typo3.org/45825


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>