Remove flags for GSF Experiment Phase 1

These flags (com.android.systemui.gsf_bouncer,
com.android.systemui.gsf_quick_settings) were part of the experimental
first phase of GSF implementation. Since we have now gathered the
trunkfood-50 metrics needed, the changes have been removed and the flags
are rolled back. There are no longer any references to these
experimental flags, so we can delete them as per the guidance in
go/android-flags-guidelines#abandoned-flags.

Flag: EXEMPT removing flags
Bug: 379364381
Test: N/A
Change-Id: I125f9ef51583d1559ee91195327fea5bcfa86b6f