[BUGFIX] Framework::getDatabaseConnection must not be protected

Resolves: #63845

Change-Id: I10094dbcf62e80a1869a24304c29200d7c440839
Reviewed-on: http://review.typo3.org/35445
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>