MC-5405: Column Minimum Height Issues

- revert removing 1px transparent border on content types due to incompatibility with selenium doNotSeeElement
- revert Tab border top fixes

Author: anthoula

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/_preview.less

@@ -225,6 +225,7 @@
     -moz-transition: box-shadow 200ms ease 200ms;
     -o-transition: box-shadow 200ms ease 200ms;
     -webkit-transition: box-shadow 200ms ease 200ms;
+    border: 1px solid transparent;
     box-shadow: 0 0 0 1px rgba(153, 153, 153, 0);
     box-sizing: border-box;
     position: relative;

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

@@ -25,12 +25,12 @@
             background: @color-white;
             content: '';
             height: 1px;
-            left: 0;
+            left: -1px;
             opacity: 1;
             position: absolute;
-            top: -1px;
+            top: -2px;
             visibility: visible;
-            width: 100%;
+            width: calc(~'100% + 2px');
             z-index: auto;
         }