Remove the rtl condition

The `rtl` condition was a mistake and completely unnecessary

Author: engelfrost

slick/slick.js

@@ -1062,16 +1062,12 @@
         }
 
         if (_.options.centerMode === true && _.slideCount <= _.options.slidesToShow) {
-            if (_.options.rtl === true) {
-                _.slideOffset = ((_.slideWidth * -Math.floor(_.options.slidesToShow)) / 2) + ((_.slideWidth * _.slideCount) / 2);
-            } else {
-                _.slideOffset = ((_.slideWidth * Math.floor(_.options.slidesToShow)) / 2) - ((_.slideWidth * _.slideCount) / 2);
-            }
+             _.slideOffset = ((_.slideWidth * Math.floor(_.options.slidesToShow)) / 2) - ((_.slideWidth * _.slideCount) / 2);
         } else if (_.options.centerMode === true && _.options.infinite === true) {
-            _.slideOffset += _.slideWidth * Math.floor(_.options.slidesToShow / 2) - _.slideWidth;
+             _.slideOffset += _.slideWidth * Math.floor(_.options.slidesToShow / 2) - _.slideWidth;
         } else if (_.options.centerMode === true) {
-            _.slideOffset = 0;
-            _.slideOffset += _.slideWidth * Math.floor(_.options.slidesToShow / 2);
+             _.slideOffset = 0;
+             _.slideOffset += _.slideWidth * Math.floor(_.options.slidesToShow / 2);
         }
 
         if (_.options.vertical === false) {