[Foundation] Fix availability attributes to be the same for all platf…

…orms. (#17002)

Don't put availability attributes inside a platform condition, because we need
all availability attributes to be visible when building all platforms,
otherwise we won't generate the correct attributes for other platforms.

src/foundation.cs

@@ -11818,29 +11818,29 @@ partial interface NSValue : NSSecureCoding, NSCopying {
 		[Static]
 		NSValue FromCGPoint (CGPoint point);
 
+		[Mac (10, 0)]
+		[MacCatalyst (15, 0)]
 #if MONOMAC
-		[Mac (10,0)]
 		[Export ("rectValue")]
 #else
-		[MacCatalyst (15, 0)]
 		[Export ("CGRectValue")]
 #endif
 		CGRect CGRectValue { get; }
 
+		[Mac (10, 0)]
+		[MacCatalyst (15, 0)]
 #if MONOMAC
-		[Mac (10,0)]
 		[Export ("sizeValue")]
 #else
-		[MacCatalyst (15, 0)]
 		[Export ("CGSizeValue")]
 #endif
 		CGSize CGSizeValue { get; }
 
+		[Mac (10, 0)]
+		[MacCatalyst (15, 0)]
 #if MONOMAC
-		[Mac (10,0)]
 		[Export ("pointValue")]
 #else
-		[MacCatalyst (15, 0)]
 		[Export ("CGPointValue")]
 #endif
 		CGPoint CGPointValue { get; }