HWC2OnFbAdapter: don't claim present fences work

We never produce real present fences, so indicate this to the
compositor. This will prevent GOOGLE_display_timing & friends from being
exposed in the client APIs.

Similar to previous change in HWC2On1Adapter.

Bug: b/111505197
Change-Id: I601a7f5628d4b218431fc0f1abb4807c9941ce64