removed Swift 4.2 helper funtion insertions

Sources/Extensions/Motion+CALayer.swift

@@ -338,8 +338,3 @@ fileprivate extension CALayer {
     }
   }
 }
-
-// Helper function inserted by Swift 4.2 migrator.
-fileprivate func convertToCAMediaTimingFillMode(_ input: String) -> CAMediaTimingFillMode {
-	return CAMediaTimingFillMode(rawValue: input)
-}

Sources/Transition/MotionTransition.swift

@@ -722,8 +722,3 @@ internal extension MotionTransition {
     }
   }
 }
-
-// Helper function inserted by Swift 4.2 migrator.
-fileprivate func convertToCAMediaTimingFillMode(_ input: String) -> CAMediaTimingFillMode {
-	return CAMediaTimingFillMode(rawValue: input)
-}