THRIFT-4902: Swift 4 and 5 compatibility (#1827)

diff --git a/lib/swift/Sources/TFramedTransport.swift b/lib/swift/Sources/TFramedTransport.swift
index ca385d6..59855eb 100644
--- a/lib/swift/Sources/TFramedTransport.swift
+++ b/lib/swift/Sources/TFramedTransport.swift
@@ -92,10 +92,10 @@
 
   private func encodeFrameSize(size: UInt32) -> Data {
     var data = Data()
-    data.append(Data(bytes: [UInt8(0xff & (size >> 24))]))
-    data.append(Data(bytes: [UInt8(0xff & (size >> 16))]))
-    data.append(Data(bytes: [UInt8(0xff & (size >> 8))]))
-    data.append(Data(bytes: [UInt8(0xff & (size))]))
+    data.append(Data([UInt8(0xff & (size >> 24))]))
+    data.append(Data([UInt8(0xff & (size >> 16))]))
+    data.append(Data([UInt8(0xff & (size >> 8))]))
+    data.append(Data([UInt8(0xff & (size))]))
 
     return data
   }