[TASK] Add pdo_sqlite to list of additional PHP extensions

TYPO3 now supports SQLite as the DBMS, if PHP module "pdo_sqlite" is
installed and enabled in the system. This change adds the module to
the list of "additional PHP extensions" in file INSTALL.md as an
optional component.
Another outdated line is removed with the patch.

Resolves: #86079
Releases: master
Change-Id: Ic91166e0482bbb80b02937361e2863e9199cae67
Reviewed-on: https://review.typo3.org/58120


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Michael Schams <typo3@2018.schams.net>
Tested-by: Michael Schams <typo3@2018.schams.net>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>