[5.1.x] Fixed #35841 -- Restored support for DB-IP databases in GeoIP2.

Thanks Felix Farquharson for the report and Claude Paroz for the
review.

Regression in 40b5b1596f.

Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

Backport of 3fad712a91 from main.

tests/gis_tests/data/geoip2/README.md

@@ -12,3 +12,17 @@ Updates can be found in [this repository][1].
 
 [0]: https://github.com/maxmind/MaxMind-DB/blob/main/LICENSE-MIT
 [1]: https://github.com/maxmind/MaxMind-DB/tree/main/test-data
+
+# DB-IP Lite Test Databases
+
+The following test databases are provided under [this license][2]:
+
+- `dbip-city-lite-test.mmdb`
+- `dbip-country-lite-test.mmdb`
+
+They have been modified to strip them down to a minimal dataset for testing.
+
+Updates can be found at [this download page][3] from DB-IP.
+
+[2]: https://creativecommons.org/licenses/by/4.0/
+[3]: https://db-ip.com/db/lite.php