remove Objective-C header stub

-#import <Flutter/Flutter.h>
-
-@interface MobileScannerPlugin : NSObject<FlutterPlugin>
-@end

-#import "MobileScannerPlugin.h"
-#if __has_include(<mobile_scanner/mobile_scanner-Swift.h>)
-#import <mobile_scanner/mobile_scanner-Swift.h>
-#else
-// Support project import fallback if the generated compatibility header
-// is not copied when this plugin is created as a library.
-// https://forums.swift.org/t/swift-static-libraries-dont-copy-generated-objective-c-header/19816
-#import "mobile_scanner-Swift.h"
-#endif
-
-@implementation MobileScannerPlugin
-+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
-  [SwiftMobileScannerPlugin registerWithRegistrar:registrar];
-}
-@end