Update default Rails version in Docker config

There is an incompatibility between our test suite and Rails versions `<
7.1.0`, so we provide `7.1.0` as the new default version.

Co-authored-by: An Stewart <andrew@super.gd>

docker-compose.yml

@@ -34,7 +34,7 @@ services:
       CAPYBARA_DRIVER: selenium_chrome_headless_docker_friendly
       DB_USERNAME: root
       DB_PASSWORD: password
-      RAILS_VERSION: ${RAILS_VERSION:-~> 7.0.2}
+      RAILS_VERSION: ${RAILS_VERSION:-~> 7.1.0}
       DB_ALL: "1"
       DB_MYSQL_HOST: mysql
       DB_POSTGRES_HOST: postgres