MC-13925: Hard Coded Margins On individual Button

- Removed hard coded 1px border from button items
- Moved default margin of button item to link data-element from pagebuilder-button-item class

Author: Hwashiang Yu

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

@@ -9,8 +9,8 @@
 
 .pagebuilder-content-type {
     .pagebuilder-button-item {
+        border: none;
         font-size: 0;
-        margin: 0 10px 10px 0;
         max-width: 100%;
         width: auto;
         z-index: auto;
@@ -26,6 +26,7 @@
         }
 
         a[data-element='link'] {
+            margin: 0 10px 10px 0;
             max-width: 100%;
             min-width: 0;
             position: relative;