The AJAX url for retrieving a new encryption key contains
two question marks. This causes the request to fail.

Fix this by removing the superflous ? from the parameters.

Resolves: #59034
Releases: 6.1, 4.7, 4.5
Change-Id: Iab3833f50a48b71b25cf0205f7eb8d6b57dd859a
Reviewed-on: https://review.typo3.org/30543
Reviewed-by: Markus Klein
Tested-by: Markus Klein