fix(acceptance): fix running acceptance tests against host on Linux (#3358)

Add an entry host.docker.internal -> host-gateway entry to the
acceptable tests container in tests/acceptance/docker/src/acceptance.yml
in order to be able to run them against an opencloud server running on
the host on Linux as well.

Reference: https://www.baeldung.com/ops/docker-compose-add-host

tests/acceptance/docker/src/acceptance.yml

@@ -16,6 +16,8 @@ services:
       EMAIL_PORT: 9000
     env_file:
       - ../../../../.woodpecker.env
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
     volumes:
       - ./run-tests.sh:/test/run-tests.sh
       - ../../../../:/woodpecker/src/github.com/opencloud-eu/opencloud