[TASK] Disable functional tests

Extbase ships with a functional test class "FileContextTest" which
contains 10 tests. All those test fail currently.

The core does not (yet) have a strategy for functional tests.
As an intermediate solution, disable the functional tests.

They can be reactivated later if the core found a general concept for
functional tests.

Resolves: #47026
Releases: 6.1,6.0
Change-Id: I53136a8ac0e902658889daed12934340c88374fd
Reviewed-on: https://review.typo3.org/19733
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Frans Saris
Tested-by: Frans Saris
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn