fixed border color of stage selector

Author: LiFaytheGoblin

src/components/stage-selector/stage-selector.css

@@ -4,6 +4,7 @@
 $header-height: calc($stage-menu-height - 2px);
 
 .stage-selector {
+    background-clip: padding-box;
     display: flex;
     flex-direction: column;
     align-items: center;