update ::before style

app.css

@@ -180,7 +180,7 @@
   border-bottom: 1px solid rgba(0, 0, 0, 0.15);
   border-left: 0;
   border-bottom: 0;
-  padding: 4px 8px;
+  padding: 6px 12px;
 }
 
 .problem-input-markdown .problem-input-markdown {
@@ -191,4 +191,5 @@
 .problem-input-markdown .problem-input-markdown::before {
   content: "";
   border: none;
+  display: none;
 }