docs: Change how code blocks look

docs/stylesheet.css

@@ -64,15 +64,13 @@ body {
 }
 
 .contents .fragment {
-	padding: 5px;
+	padding: 15px;
 	background-color: #444;
-	border: solid 1px rgba(255, 255, 255, 0.2);
+	border: none;
 }
 
 .contents .fragment .lineno {
-	background-color: #333;
-	border: none;
-	padding-right: 10px;
+	display: none;
 }
 
 .contents code {