Revert "Add "Example" label to example code blocks"

This reverts commit 69fc9ce.

Author: st0012

lib/rdoc/generator/template/darkfish/css/rdoc.css

@@ -601,24 +601,6 @@ main .method-source-code.active-menu {
   max-height: 100vh;
 }
 
-main pre.ruby::before {
-  content: "Example";
-  color: var(--secondary-color);
-  border-bottom: 1px solid var(--border-color);
-  display: block;
-  padding: 10px 0;
-  font-size: 0.9em;
-  margin-bottom: 10px;
-}
-
-main pre.ruby {
-  margin: 0;
-  padding: 0px 16px 16px 16px;
-  overflow-x: auto;
-  border-radius: 4px;
-  border-color: var(--border-color);
-}
-
 main .method-description .method-calls-super {
   color: var(--text-color);
   font-weight: bold;