[BUGFIX] Fix misspelling in RTE meta menu

Corrects the label for inserting unordered bullet lists.

Fixes: #43886
Releases: 6.1, 6.0, 4.7, 4.6, 4.5
Change-Id: I4190dbcc8cadc90ae00d1ec1aa405a5a75863594
Reviewed-on: https://review.typo3.org/17956
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn