Remove deprecation notice from README.md

[jhasse]

Since #532 has been fixed, this can be removed.

[rennis250]

Any reason why this has been skipped?

[rennis250]

?

[tomaka]

Glium is still not really maintained, so I don't see why this text should be removed.

[jhasse]

You said that "My personal rule is to grant the collaborator status to all people who have contributed to the core of the library. And once people are collaborators, I encourage them to also review and merge PRs."

I think once some people start reviewing and merging PRs someone from them could take over maintaining.

[porky11]

But I think, this part of the message can be removed, since it is in an own organisation

If you use Glium and would be interested in seeing it moved to its own organisation, you can express your interest here.

[paulirotta]

Yes, @tomaka does outstanding work. If his focus remains elsewhere, it might ease his burden if there is someone else who can help with glium PRs. Vulkan is still sadly not supported on Intel devices in a meaningful way so...