fix(content): hide overflow of expandable section and accordion content (#2944)

Author: engai

ui/components/accordion/base/_index.scss

@@ -103,6 +103,7 @@
  * @required
  */
 .slds-accordion__content {
+  overflow: hidden;
   visibility: hidden;
   opacity: 0;
   height: 0;
@@ -126,6 +127,7 @@
   }
 
   > .slds-accordion__content {
+    overflow: visible;
     visibility: visible;
     opacity: 1;
     height: auto;

ui/components/expandable-section/base/_index.scss

@@ -62,6 +62,7 @@
    * @restrict .slds-section div
    */
   &__content {
+    overflow: hidden;
     visibility: hidden;
     opacity: 0;
     height: 0;
@@ -88,6 +89,7 @@
 
     .slds-section__content {
       padding-top: $spacing-small;
+      overflow: visible;
       visibility: visible;
       opacity: 1;
       height: auto;