fix bug in case statement, allow jpg and jpeg (#5473)

the current implementation does not work if one specifies "jpg", it works only with "jpeg" due to the || syntax used. 
This is a proposal to fix it.

tns-core-modules/image-source/image-source.ios.ts

@@ -185,10 +185,11 @@ function getFileName(path: string): string {
 function getImageData(instance: UIImage, format: "png" | "jpeg" | "jpg", quality = 1.0): NSData {
     var data = null;
     switch (format) {
-        case "png": // PNG
+        case "png":
             data = UIImagePNGRepresentation(instance);
             break;
-        case "jpeg" || "jpg": // JPEG
+        case "jpeg":
+        case "jpg":
             data = UIImageJPEGRepresentation(instance, quality);
             break;
     }