tweak popover dropshadows

frontend/src/metabase/components/Popover.css

@@ -9,7 +9,7 @@
   pointer-events: auto;
   min-width: 1em; /* ewwwwwwww */
   border: 1px solid #ddd;
-  box-shadow: 0 1px 7px rgba(0, 0, 0, 0.18);
+  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
   background-color: #fff;
   border-radius: 4px;
   display: flex;