[TASK] bamboo: Use yarn instead of npm install

With the switch from npm install to yarn install we
forgot to adapt the test suites. Update plan specs.

Change-Id: Ibced9d53a4abf73b33e95027a61263f19cd94e56
Resolves: #83544
Related: #83038
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/55336


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>