Update ldap.md

If you escape the '\' character when using a "domain\user" scheme for the bind_dn name, it will fail. gitlab-ctl reconfigure escapes characters, and if you pre-escape the '\', the resultant yaml file will have four (4) '\' characters.

doc/administration/auth/ldap.md

@@ -111,7 +111,7 @@ main:
   uid: 'sAMAccountName' # This should be the attribute, not the value that maps to uid.
 
   ##
-  ## Examples: 'america\\momo' or 'CN=Gitlab Git,CN=Users,DC=mydomain,DC=com'
+  ## Examples: 'america\momo' or 'CN=Gitlab Git,CN=Users,DC=mydomain,DC=com'
   ##
   bind_dn: '_the_full_dn_of_the_user_you_will_bind_with'
   password: '_the_password_of_the_bind_user'