Revert "Add experiment flag for tethering refactor"

This reverts commit cf11be9eb2c7b727594ff515c8e2584cdca854ba.

Reason for revert: avoid some IpServer(s) running the new sync state machine while others use the async state machine.

Bug: 319212113
Change-Id: Ib086a7ccd102f38e579c79f94aceae9971f1853a
3 files changed