README regen triggered by 2.6.21 release(s)

Author: github-actions[bot]

README.md

@@ -5,7 +5,7 @@
 -	[`3.0.8`, `3.0`](https://github.com/haproxytech/haproxy-docker-ubuntu-quic/blob/main/3.0/Dockerfile)
 -	[`2.9.14`, `2.9`](https://github.com/haproxytech/haproxy-docker-ubuntu-quic/blob/main/2.9/Dockerfile)
 -	[`2.8.14`, `2.8`](https://github.com/haproxytech/haproxy-docker-ubuntu-quic/blob/main/2.8/Dockerfile)
--	[`2.6.20`, `2.6`](https://github.com/haproxytech/haproxy-docker-ubuntu-quic/blob/main/2.6/Dockerfile)
+-	[`2.6.21`, `2.6`](https://github.com/haproxytech/haproxy-docker-ubuntu-quic/blob/main/2.6/Dockerfile)
 
 # Quick reference