[BUGFIX] Fix wording of encryption key in Installer

The description of the encryption key uses the irregular verb
'output' in the wrong way.

Resolves: #54677
Releases: 6.2
Change-Id: Iad5cf8fea6e57cd8449da6d93edd7d05b3b52bf8
Reviewed-on: https://review.typo3.org/26611
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind