remove border on code roles

Author: tony

doc/_static/libtmux.css

@@ -47,10 +47,9 @@ code.literal {
   color: #24292e;
   box-sizing: border-box;
   display: inline-block;
-  padding: 0 5px;
+  padding: 0;
   background: #fafcfc;
   border: 1px solid #f0f4f7;
-  border-radius: 4px;
   line-height: 20px;
 }