v3.4.0

**This is a rollback release to a stable v3.2.0 state**

This should fix any stability issues you might be having with v3.3.0.

## More info:

There were some stability issues with concurrency improvements in v3.3.0.

For most of the servers it would work, but some would hang.

Tests did not catch the issue cause it worked on some setups, but not on others.

We will add more tests to figure out the exact issue but until then v3.4 will be stable.

## Updates
* Rollback code to v3.2.0 for upcoming v3.4 release by @Nedomas in https://github.com/supercorp-ai/supergateway/pull/90


**Full Changelog**: https://github.com/supercorp-ai/supergateway/compare/v3.3.0...v3.4.0