MC-2390: HTML code font-size is 14px which doesn't meet requirement

Change to 12px

Author: danmooney2

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

@@ -22,6 +22,7 @@
         .placeholder-html-code {
             background-color: @color-gray98;
             font-family: @font-family__console;
+            font-size: 12px;
             font-weight: @font-weight__light;
             height: 60px;
             overflow: hidden;