fix: prevent popover flow out of the radius limit area

packages/semi-foundation/dropdown/dropdown.scss

@@ -7,6 +7,7 @@ $module: #{$prefix}-dropdown;
 .#{$module} {
     @include font-size-regular;
     &-wrapper {
+        overflow-y:auto; // prevent flow out of the radius limit area
         @include shadow-elevated;
         position: relative;
         z-index: $z-dropdown;