[BUGFIX] Resolve typo in ClassNamingUtility description

Changes 'convertions' to 'conversions'

Resolves: #47393
Releases: 6.1
Change-Id: I98e4826527e25fdbf9da0855c05fcaa7d67698c2
Reviewed-on: https://review.typo3.org/20054
Reviewed-by: Oliver Klee
Reviewed-by: Alexander Opitz
Tested-by: Alexander Opitz
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn