MC-3706: Move Handle Not Vertically Centered On Button

- vertically center move handle

Author: krissyhiserote

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/button-item/_default.less

@@ -43,7 +43,9 @@
                 cursor: -moz-grab;
                 cursor: -webkit-grab;
                 left: 0;
+                margin-top: -(@pagebuilder-button__font-size/2);
                 position: absolute;
+                top: 50%;
 
                 &:active {
                     cursor: grabbing;
@@ -56,7 +58,6 @@
                     content: @icon-gripper__content;
                     display: inline-block;
                     font-size: @pagebuilder-button__font-size;
-                    line-height: @pagebuilder-button__line-height;
                     position: absolute;
                 }