[BUGFIX] Misspelling in scheduler documentation

Corrects certain words / phrases from the documentation manual.

Fixes: #33936
Releases: 6.1, 6.0
Change-Id: I89ad923280cd1df6d126884e88987abaa9d5f7df
Reviewed-on: https://review.typo3.org/17983
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn