Remove write-only bridge from sample legacy modules (#59261)

Summary:
Pull Request resolved: #59261

RCTSampleLegacyModule on iOS and macOS stored a bridge that nothing reads. Delete the ivar and setter from both sample files.

Changelog:
[Internal]

Reviewed By: shwanton

Differential Revision: D126575656

fbshipit-source-id: 24554aa151537a14afd4f57ef8de5b5e465933c4

Author: christophpurrer

packages/react-native/ReactCommon/react/nativemodule/samples/platform/ios/ReactCommon/RCTSampleLegacyModule.mm

@@ -7,9 +7,7 @@
 
 #import "RCTSampleLegacyModule.h"
 
-@implementation RCTSampleLegacyModule {
-  RCTBridge *_bridge;
-}
+@implementation RCTSampleLegacyModule
 
 // Backward-compatible export
 RCT_EXPORT_MODULE()
@@ -20,11 +18,6 @@ + (BOOL)requiresMainQueueSetup
   return YES;
 }
 
-- (void)setBridge:(RCTBridge *)bridge
-{
-  _bridge = bridge;
-}
-
 - (dispatch_queue_t)methodQueue
 {
   return dispatch_get_main_queue();