Remove mention of -Xincremental from CodeServer options' help

Follow-up to 6c2cc42ecfe8c4640f71998c5b7cef447ebae351 which removed
the -Xincremental flag but forgot to update this small piece of doc
referencing it.

Change-Id: Iec47df6d53e15b8840f4c18a0a301e49d758cf17
1 file changed