[TASK] Completely remove folder "tests"

Due to wrong git settings on my local mashine
I committed both "tests" and "Tests" some time ago.
Only "Tests" is actually needed.

Information: This change has already been made on master.

Releases: 1.9
Fixes: #60927
Change-Id: I1924db9e809af97989d52a1a6d12e8d5e7ac47b4
Reviewed-on: http://review.typo3.org/32121
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>