[FIX] http_routing: leftover old geoip resolver

The geoip resolver was moved from http_routing to code/http.py in #86015
and is always available since then. The `_geoip_resolver` global
variable is a leftover we forgot to remove.

Backport to 16.0 of saas-16.1 270672da

closes odoo/odoo#124319

Signed-off-by: Julien Castiaux (juc) <juc@odoo.com>