tour: fix bad backticks with space in it

CL 113998 changed

  drop the ", value" entirely

into

  drop the `, value` entirely.

in moretypes.article, but that's not rendered correctly because the
backspaces have a space in it, which is not allowed. Screenshot:

https://i.imgur.com/dDXNl6X.png

Keep the backticks, but take the space out.

Change-Id: If702d69d2d0086bcfca7b14f8e020a8c152edf36
Reviewed-on: https://go-review.googlesource.com/123235
Reviewed-by: Andrew Bonventre <andybons@golang.org>
diff --git a/content/moretypes.article b/content/moretypes.article
index 086a513..2840489 100644
--- a/content/moretypes.article
+++ b/content/moretypes.article
@@ -247,7 +247,7 @@
 
 You can skip the index or value by assigning to `_`.
 
-If you only want the index, drop the `, value` entirely.
+If you only want the index, drop the `,` `value` entirely.
 
 .play moretypes/range-continued.go