Correct tvOS availability for Float16 in _TestSupport.

Author: stephentyrone

Sources/_TestSupport/RealTestSupport.swift

@@ -16,7 +16,7 @@ where Exponent: FixedWidthInteger,
       RawSignificand: FixedWidthInteger { }
 
 #if !((os(macOS) || targetEnvironment(macCatalyst)) && arch(x86_64))
-@available(macOS 11.0, iOS 14.0, watchOS 14.0, tvOS 7.0, *)
+@available(macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0, *)
 extension Float16: FixedWidthFloatingPoint { }
 #endif