[CoreText] Adopt XAMCORE_4_0 changes in .NET. (#13943)

src/CoreText/CTFontManager.cs

@@ -60,14 +60,8 @@ namespace CoreText {
 		[UnsupportedOSPlatform ("maccatalyst")]
 #endif
 		Session = 3,
-#if !XAMCORE_4_0
 #if !NET
 		[NoiOS][NoTV][NoWatch] // historically not available under the old name
-#else
-		[UnsupportedOSPlatform ("tvos")]
-		[UnsupportedOSPlatform ("ios")]
-		[UnsupportedOSPlatform ("maccatalyst")]
-#endif
 		User = Persistent,
 #endif
 	}
@@ -446,16 +440,16 @@ namespace CoreText {
 			return ret;
 		}
 		
+#if !NET
 		static CTFontManager ()
 		{
 			var handle = Libraries.CoreText.Handle;
 #if !XAMCORE_3_0
 			ErrorDomain  = Dlfcn.GetStringConstant (handle, "kCTFontManagerErrorDomain");
 #endif
-#if !XAMCORE_4_0
 			ErrorFontUrlsKey  = Dlfcn.GetStringConstant (handle, "kCTFontManagerErrorFontURLsKey");
-#endif
 		}
+#endif // !NET
 
 		static NSString _RegisteredFontsChangedNotification;
 
@@ -473,7 +467,7 @@ namespace CoreText {
 #if !XAMCORE_3_0
 		public readonly static NSString ErrorDomain;
 #endif
-#if !XAMCORE_4_0
+#if !NET
 		[Obsolete ("Use the 'CTFontManagerErrorKeys.FontUrlsKey' property instead.")]
 		public readonly static NSString ErrorFontUrlsKey;
 #endif