Remove Docker image release v1.9999999

[immanuelfodor]

https://github.com/element-hq/synapse/pkgs/container/synapse/554802967?tag=v1.9999999

This version messes up semver releases and Docker image updates as it's higher than the current "real" release of v1.140.0.

Please remove tag v1.9999999

[anoadragon453]

Apologies, this was accidentally pushed while testing this PR against a fork: #19096. The release script pushed a v1.9999999 tag to this repo, and then subsequent actions created a docker image and pushed it to Docker Hub and GHCR.

We'll go ahead and delete those images now.

[anoadragon453]

Both images have now been removed from the registries. Apologies again, and thanks for creating an issue!

[immanuelfodor]

Thank you very much for the quick action, much appreciated! 🙏