Revert "[BUGFIX] Simulate submit button for rsaauth form submit"

This reverts commit 1bd63f45.

This change caused a regression which basically affected users of Mozilla
Firefox - details are described in issue #84503. Besides that the initial
bug report address the frontend part, changing backend login behavior was
not required in order for the bug fix.

Releases: master, 8.7, 7.6
Resolves: #84503
Reverts: #76120
Change-Id: I45fe6086afa48eed71be635e8cf4a1f3fa138ab2
Reviewed-on: https://review.typo3.org/56396


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>