pass-secret-service: add GNUPGHOME to service env vars

This is nescesarry for non-default locations, and without it, many
programs like element-desktop break in very confusing ways.

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

modules/services/pass-secret-service.nix

@@ -58,6 +58,7 @@ in {
               optionalString (cfg.storePath != null) "--path ${cfg.storePath}"
             }";
           BusName = busName;
+          Environment = [ "GNUPGHOME=${config.programs.gpg.homedir}" ];
         };
 
         Install.WantedBy = [ "default.target" ];