Flip the bincompat switches on the tightened casting semantics

so the new behavior is always enabled by default on all OSes.

(This may change depending on whether anyone is actually depending
on this behavior.)

Author: tbkka

stdlib/public/runtime/Bincompat.cpp

@@ -189,7 +189,7 @@ bool useLegacyOptionalNilInjectionInCasting() {
 // by that protocol.
 bool useLegacyObjCBoxingInCasting() {
 #if BINARY_COMPATIBILITY_APPLE
-  return true; // For now, continue using the legacy behavior on Apple OSes
+  return false; // For now, always use the new behavior on Apple OSes
 #else
   return false; // Always use the new behavior on non-Apple OSes
 #endif
@@ -209,7 +209,7 @@ bool useLegacyObjCBoxingInCasting() {
 
 bool useLegacySwiftValueUnboxingInCasting() {
 #if BINARY_COMPATIBILITY_APPLE
-  return true; // For now, continue using the legacy behavior on Apple OSes
+  return false; // For now, always use the new behavior on Apple OSes
 #else
   return false; // Always use the new behavior on non-Apple OSes
 #endif