fix: update minio health check

[r-o-b-o-t-o]

• [X] I understand and have followed the contribution guide
• [X] I have tested my changes locally and they are working as intended

This PR fixes the createbuckets service. curl is not available in the minio/mc image anymore, it can be replaced with the mc ready command.

Probably fixes https://github.com/revoltchat/self-hosted/issues/76

[r-o-b-o-t-o]

Oops, looks like renaming a fork's branch actually deletes and recreates it 🙄