[BUGFIX] BE login template: fix invalid HTML structure

In the backend login template a div tag is nested within a dl tag.
This is prohibited by the HTML specification.
This patch reverses the tag ordering.

Resolves: #61962
Releases: master, 6.2
Change-Id: I4e6410111a2ede2f9294cf390d7e96eedbeb58f6
Reviewed-on: http://review.typo3.org/33078
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>