These docs were misleading for package installations of
Elasticsearch. Instead, we should refer to $ES_CONFIG/ingest-geoip as
the path to place the custom database files. For non-package
installations, this is the same as $ES_HOME/config, but for package
installations this is not the case as the config directory for package
installations is /etc/elasticsearch, and is not relative to
$ES_HOME. This commit corrects the docs.