css fix of expanding code box in documentation (#1155)

The code sample box in Hugo code samples expanded on mouse over to 100vw which went over the sidebar toc. This solution solves this looking better and expanding only over the middle column.

_vendor/github.com/gohugoio/gohugoioTheme/assets/output/css/app.css

@@ -4828,7 +4828,7 @@ pre {
   right: 50%;*/
   /*margin-left: -30vw;*/
   margin-right: -30vw;
-  max-width: 100vw;
+  max-width: 50vw;
   }
 }
 .code-block .line-numbers-rows {