Fix tab indentation in code view (#10671)

Resolves: #5596

Signed-off-by: Alexander Scheel <alexander.m.scheel@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/less/_base.less

 
         li {
             display: block;
-            width: 100%;
-
-            &:before {
-                content: ' ';
-            }
+            width: calc(100% - 1ch);
+            margin-left: 1ch;
         }
     }
 }