update redirects

(cherry picked from commit c546f8e)

Author: ajhuh-mdb

config/redirects

@@ -1,6 +1,6 @@
 define: base https://www.mongodb.com/docs/php-library
 define: prefix docs/php-library
 raw: ${prefix}/ -> ${base}/current
-define: version v1.1 v1.2 v1.3 v1.4 v1.5 v1.6 v1.7 v1.8 v1.9 v1.10 v1.11 v1.12 v1.13 master
+define: version v1.1 v1.2 v1.3 v1.4 v1.5 v1.6 v1.7 v1.8 v1.9 v1.10 v1.11 v1.12 v1.13 v1.15 master
 symlink: upcoming -> master
-symlink: current -> v1.13
+symlink: current -> v1.15