[HealthKit] Remove HKSeriesBuilder compliance of NSSecureCoding. (#17302)

There's no trace of this in the headers, so I assume it's something that
happened in a beta and then got removed, and we didn't notice to update our
bindings.

src/healthkit.cs

@@ -3501,7 +3501,7 @@ namespace HealthKit {
 	[BaseType (typeof (NSObject))]
 	[DisableDefaultCtor]
 	interface HKSeriesBuilder
-#if !MONOMAC
+#if !MONOMAC && !XAMCORE_5_0
 		: NSSecureCoding
 #endif
 {