Don't disable rust modules for linux_bionic

With If4300583edfb6d75bd4d984b38f73b6a406b4447, linux_bionic supports
arm64 and rust toolchain was configured to support the new target.
However, rust module types still have been disabled for linux_bionic
targets which forces many rust modules to be annotated with
target.linux_bionic_arm64.enabled: true, which will be very cumbersome.
Therefore, stop disabling the rust modules for linux_bionic.

Bug: 159685774
Test: HOST_CROSS_OS=linux_bionic m nothing
Change-Id: I68b97a43e8252fb82da6e87b3481fa237e1f2691

rust/rust.go

@@ -559,21 +559,6 @@ func (mod *Module) Init() android.Module {
 	android.InitAndroidArchModule(mod, mod.hod, mod.multilib)
 
 	android.InitDefaultableModule(mod)
-
-	// Explicitly disable unsupported targets.
-	android.AddLoadHook(mod, func(ctx android.LoadHookContext) {
-		disableTargets := struct {
-			Target struct {
-				Linux_bionic struct {
-					Enabled *bool
-				}
-			}
-		}{}
-		disableTargets.Target.Linux_bionic.Enabled = proptools.BoolPtr(false)
-
-		ctx.AppendProperties(&disableTargets)
-	})
-
 	return mod
 }