Modify the lowerCamelCase the Case of Enum.

Author: nohirap

test/Sema/Inputs/enum_multi_file_helper.swift

@@ -1,16 +1,16 @@
 enum Foo : Int {
-  case A = 0
+  case a = 0
 }
 
 enum Bar : UInt {
-  case A = 0
-  case B = 22
+  case a = 0
+  case b = 22
 }
 
 enum Baz : UInt {
-  case A = 0
+  case a = 0
 }
 
 enum Garply : String {
-    case A = "A"
+    case a = "A"
 }