[BUGFIX] Revert "[TASK] Use a 401 header if login is not successful"

This reverts commit 9974f36d2736e21875a76d33a9dd7ceb440a100d.

The 401 header code is used with HTTP based authentication schemes,
based on RFC 2617.

This is not the case here.

Resolves: #55966
Reverts: #51803
Releases: 6.2, 6.1, 6.0, 4.5
Change-Id: I134f0f1d575f3e8d4c37c2af62df8eca3f01f817
Reviewed-on: https://review.typo3.org/27888
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert