MTRDeviceControllerOverXPC should inherit from MTRDeviceController_Concrete for now. (#35685)

That's what it used to do, and for now we should just leave it be.  Longer-term,
we need to figure out what should happen with MTRDeviceControllerOverXPC;
whether it should inherit from the base MTRDeviceController, or just not exist,
or what.
diff --git a/src/darwin/Framework/CHIP/MTRDeviceControllerOverXPC.h b/src/darwin/Framework/CHIP/MTRDeviceControllerOverXPC.h
index 9616e22..669baea 100644
--- a/src/darwin/Framework/CHIP/MTRDeviceControllerOverXPC.h
+++ b/src/darwin/Framework/CHIP/MTRDeviceControllerOverXPC.h
@@ -16,7 +16,8 @@
  */
 
 #import <Matter/MTRDefines.h>
-#import <Matter/MTRDeviceController.h>
+
+#import "MTRDeviceController_Concrete.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -24,7 +25,7 @@
 
 typedef NSXPCConnection * _Nonnull (^MTRXPCConnectBlock)(void);
 
-@interface MTRDeviceControllerOverXPC : MTRDeviceController
+@interface MTRDeviceControllerOverXPC : MTRDeviceController_Concrete
 
 - (instancetype)init NS_UNAVAILABLE;
 + (instancetype)new NS_UNAVAILABLE;