style: do not style stderr as red (#7472)

Diagnostic output is often written to stderr, and the red color can be
alarming.

Author: akshayka

frontend/src/components/editor/output/Outputs.css

@@ -47,19 +47,15 @@
   font-size: 0.813rem;
 }
 
-.marimo-error,
-.stderr {
-  font-weight: bold;
-
-  @apply text-error;
-}
-
 .marimo-error {
   background: #ffc0cb30;
   padding: 3%;
   font-size: 0.8125rem;
+  font-weight: bold;
   border-radius: 20px;
   white-space: pre-wrap; /* respect newlines */
+
+  @apply text-error;
 }
 
 .marimo-json-output {