refactor: Remove unnecessary knob bottom margin

Author: rkunev

src/ColorPicker.vue

@@ -351,9 +351,9 @@
  /*
  * "2.5%" adds distance from the top edge of the rotator to center the knob inside the gradient ring
  * "auto" centers the knob horizontally inside the rotator plane
- * the bottom value of 0 is added just to levarage the margin shorthand syntax
  */
- margin: 2.5% auto 0;
+ margin-top: 2.5%;
+ margin-inline: auto;
 
  background-color: #fff;
  transition: transform 0.4s cubic-bezier(0.35, 0, 0.25, 1);