update prolem markdown style

app.css

@@ -161,12 +161,17 @@
 .problem-input-markdown::before {
   content: "Problem rendered";
   border: 1px solid rgba(0, 0, 0, 0.15);
-  border-radius: 10px;
+  border-radius: 0 10px 0 0px;
   position: absolute;
   left: 0;
   top: 0;
   border-right: 1px solid rgba(0, 0, 0, 0.15);
   border-bottom: 1px solid rgba(0, 0, 0, 0.15);
+  padding: 4px 8px;
+}
+
+.problem-input-markdown .problem-input-markdown {
+  border: none;
 }
 
 .problem-input-markdown .problem-input-markdown::before {