update robots.txt disallow

Allows projects in groups starting with "s" while still disallowing the
snippets short urls.

CHANGELOG

@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.13.0 (unreleased)
   - Speed-up group milestones show page
+  - Fix robots.txt disallowing access to groups starting with "s" (Matt Harrison)
 
 v 8.12.1 (unreleased)
 

public/robots.txt

@@ -23,7 +23,7 @@ Disallow: /groups/*/edit
 Disallow: /users
 
 # Global snippets
-Disallow: /s
+Disallow: /s/
 Disallow: /snippets/new
 Disallow: /snippets/*/edit
 Disallow: /snippets/*/raw