fix(planner): dropdown menu overlap with the menu button (#3742)

This is a fix for a specific case where the top module is a one-liner. Removed z-index: 1 from .menuBtn in PlannerModule.scss

Author: iZUMi-kyouka

website/src/views/planner/PlannerModule.scss

@@ -57,7 +57,6 @@
 
 .menuBtn {
   position: relative;
-  z-index: 1;
   float: right;
   margin: -0.3rem -0.3rem 0 0;