fix(css): distinguish code/pre from #message

rhodecode/public/css/legacy_code_styles.less

@@ -287,10 +287,18 b' div.markdown-block #message {'
     font-family: @text-monospace;
     font-size: 11px;
     .border-radius(@border-radius);
-    background-color: transparent;
     color: @grey3;
 }
 
+div.markdown-block code,
+div.markdown-block pre {
+    background-color: transparent;
+}
+
+div.markdown-block #ws,
+div.markdown-block #message {
+    background-color: white;
+}
 
 div.markdown-block code {
     border: @border-thickness solid @grey6;