Turn off the new back arrow in Teamfood.

We're still in the middle of making fairly non-trivial changes to the
new Back Arrow, and it's expected that there might be regressions, or
misc changes that affect its current look+feel.

To avoid confusing folks with such random changes, we're disabling it in
Teamfood for now. The medium-to-long-term goal is to migrate the
UX prototype from its plugin incarnation into production-level code that
lives in this repo (which is when we'll re-enable it).

Bug: 241248730
Test: Manual
Change-Id: I1918008f15f47cfb0f3378462bc168d0bcd8e485

packages/SystemUI/src/com/android/systemui/flags/Flags.java

@@ -208,7 +208,7 @@ public class Flags {
             new SysPropBooleanFlag(1202, "persist.wm.debug.predictive_back_always_enforce", false);
 
     public static final BooleanFlag NEW_BACK_AFFORDANCE =
-            new BooleanFlag(1203, false /* default */, true /* teamfood */);
+            new BooleanFlag(1203, false /* default */, false /* teamfood */);
 
     // Pay no attention to the reflection behind the curtain.
     // ========================== Curtain ==========================