[nominatim-web] Use set_by_lua_block to set $lang

[Bartłomiej Piotrowski <bpiotrowski src gnome org>]

commit 3083c828038c1985acf713a6cc46d97c1a2ce30f
Author: Bartłomiej Piotrowski <bpiotrowski gnome org>
Date:   Tue May 26 18:19:53 2020 +0200

    Use set_by_lua_block to set $lang

 nginx.conf | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/nginx.conf b/nginx.conf
index 5713d5a..dbd5a09 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -48,9 +48,9 @@ http {
            access_log off;
        }
 
-       if ($args ~* "accept-language\=([a-zA-z-]{1,5})") {
-           set $lang $1;
-       }
+        set_by_lua_block $lang {
+            return ngx.req.get_uri_args()["accept-language"]
+        }
 
        location /redis-fetch {
            internal;