Remove _dartobservatory._tcp legacy DNS registration type

shell/platform/darwin/ios/framework/Source/FlutterDartVMServicePublisher.mm

@@ -65,18 +65,13 @@ @interface DartVMServiceDNSServiceDelegate : NSObject <FlutterDartVMServicePubli
 
 @implementation DartVMServiceDNSServiceDelegate {
   DNSServiceRef _dnsServiceRef;
-  DNSServiceRef _legacyDnsServiceRef;
 }
 
 - (void)stopService {
   if (_dnsServiceRef) {
     DNSServiceRefDeallocate(_dnsServiceRef);
     _dnsServiceRef = NULL;
   }
-  if (_legacyDnsServiceRef) {
-    DNSServiceRefDeallocate(_legacyDnsServiceRef);
-    _legacyDnsServiceRef = NULL;
-  }
 }
 
 - (void)publishServiceProtocolPort:(NSURL*)url {
@@ -91,7 +86,6 @@ - (void)publishServiceProtocolPort:(NSURL*)url {
   uint32_t interfaceIndex = 0;
 #endif  // TARGET_IPHONE_SIMULATOR
   const char* registrationType = "_dartVmService._tcp";
-  const char* legacyRegistrationType = "_dartobservatory._tcp";
 
   const char* domain = "local.";  // default domain
   uint16_t port = [[url port] unsignedShortValue];
@@ -107,20 +101,6 @@ - (void)publishServiceProtocolPort:(NSURL*)url {
     return;
   }
 
-  // TODO(bkonyi): remove once flutter_tools no longer looks for the legacy registration type.
-  // See https://github.com/dart-lang/sdk/issues/50233
-  //
-  // Try to fallback on the legacy registration type.
-  err = DNSServiceRegister(&_legacyDnsServiceRef, flags, interfaceIndex,
-                           FlutterDartVMServicePublisher.serviceName.UTF8String,
-                           legacyRegistrationType, domain, NULL, htons(port), txtData.length,
-                           txtData.bytes, RegistrationCallback, NULL);
-
-  if (err == 0) {
-    DNSServiceSetDispatchQueue(_legacyDnsServiceRef, dispatch_get_main_queue());
-    return;
-  }
-
   FML_LOG(ERROR) << "Failed to register Dart VM Service port with mDNS with error " << err << ".";
   if (@available(iOS 14.0, *)) {
     FML_LOG(ERROR) << "On iOS 14+, local network broadcast in apps need to be declared in "