revert changes to double quotes

Author: karlasamantha

7-animation/3-js-animation/2-animate-ball-hops/solution.md

@@ -17,7 +17,7 @@ animate({
   duration: 2000,
   timing: makeEaseOut(bounce),
   draw: function (progress) {
-    ball.style.top = height * progress + 'px'
+    ball.style.top = height * progress + "px"
   }
 });
 
@@ -26,7 +26,7 @@ animate({
   duration: 2000,
   timing: makeEaseOut(quad),
   draw: function (progress) {
-    ball.style.left = width * progress + 'px'
+    ball.style.left = width * progress + "px"
   }
 });
 ```