Bump geoalchemy2 from 0.4.2 to 0.18.4

Bumps [geoalchemy2](https://github.com/geoalchemy/geoalchemy2) from 0.4.2 to 0.18.4.
- [Release notes](https://github.com/geoalchemy/geoalchemy2/releases)
- [Changelog](https://github.com/geoalchemy/geoalchemy2/blob/main/CHANGES.txt)
- [Commits](geoalchemy/geoalchemy2@0.4.2...0.18.4)

---
updated-dependencies:
- dependency-name: geoalchemy2
  dependency-version: 0.18.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ colander==2.0
 dogpile.cache==1.3.4
 elasticsearch==2.4.1
 elasticsearch_dsl==2.2.0
-geoalchemy2==0.4.2
+geoalchemy2==0.18.4
 geojson==3.2.0
 geomet==1.1.0
 kombu==5.6.1