Update JPDA documentation with respect to sync port.

This is a follow-up to commit
425673da79426d66c1ea05029f295b63d0e8a3c6
(https://android-review.googlesource.com/#/c/231590).

Bug: 28869570
Change-Id: Ieafdb48905a2ea44a4ac45635bf720b12d8c05da
2 files changed