THRIFT-5653: Update TType.uuid raw value to 16 (#2717)

Removes non-standard utf8 type with raw value 16 and replaces uuid raw value with 16
diff --git a/lib/swift/Sources/TProtocol.swift b/lib/swift/Sources/TProtocol.swift
index 87e3bc5..ed6db6f 100644
--- a/lib/swift/Sources/TProtocol.swift
+++ b/lib/swift/Sources/TProtocol.swift
@@ -40,9 +40,7 @@
   case map      = 13
   case set      = 14
   case list     = 15
-  case utf8     = 16
-  //case utf16    = 17
-  case uuid     = 17
+  case uuid     = 16
 }
 
 public protocol TProtocol {