nixos/sympa: fix PATH_INFO splitting for sympa-6.2.56

Our regex for splitting HTTP path into SCRIPT_NAME and PATH_INFO was
incorrect when webLocation was set to "/". Since Sympa 6.2.56 this has
caused the web interface to return "421 Misdirected Request".

Since 6.2.56 Sympa can do the splitting on its own so we can simply
remove it from nginx configuration.

See also:
- sympa-community/sympa#879
- sympa-community/sympa#910
- sympa-community/sympa-community.github.io#53

(cherry picked from commit bd4e4dd)

nixos/modules/services/mail/sympa.nix

@@ -513,10 +513,6 @@ in
           include ${config.services.nginx.package}/conf/fastcgi_params;
 
           fastcgi_pass unix:/run/sympa/wwsympa.socket;
-          fastcgi_split_path_info ^(${loc})(.*)$;
-
-          fastcgi_param PATH_INFO       $fastcgi_path_info;
-          fastcgi_param SCRIPT_FILENAME ${pkg}/lib/sympa/cgi/wwsympa.fcgi;
         '';
       }) // {
         "/static-sympa/".alias = "${dataDir}/static_content/";