[TASK] travis-ci: Drop JS unit tests

Drop the jasmine / karma based JS unit tests from travis. They're
becoming unstable and are executed as pre-merge tests anyway.
Supporting one executing platform that keeps an eye on
nodejs & friends should be enough.

Change-Id: Ie2134c08c50d9da33ff39bc1a0fe3f4a416e7b45
Resolves: #81192
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/52758


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>