[BUGFIX] Output dashed name for missing CLI arguments

This changes the command argument name outputted on errors from variable
naming to dashed notation as used on the CLI.

Resolves: #61630
Releases: 6.2, master
Change-Id: Ie41c90c056505df859aec3ee306718c874dd8a05
Reviewed-on: http://review.typo3.org/34449
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Markus Klein <klein.t3@reelworx.at>