Bump pixi version to v0.21.0 (#20) #30

Job	Run time
Check if version changed	5s
build (debian:bookworm-slim)	3m 19s
build (debian:bookworm)	3m 3s
build (debian:bullseye-slim)	2m 58s
build (debian:bullseye)	3m 19s
build (ubuntu:noble)	3m 2s
build (ubuntu:mantic)	3m 5s
build (ubuntu:jammy)	4m 2s
build (ubuntu:focal)	3m 1s
build (nvidia/cuda:12.3.1-base-ubuntu22.04)	3m 8s
build (nvidia/cuda:12.3.1-base-ubuntu20.04)	3m 5s
build (nvidia/cuda:12.2.2-base-ubuntu22.04)	3m 18s
build (nvidia/cuda:12.2.2-base-ubuntu20.04)	3m 14s
build (nvidia/cuda:12.1.1-base-ubuntu22.04)	3m 10s
build (nvidia/cuda:12.1.1-base-ubuntu20.04)	3m 18s
build (nvidia/cuda:11.8.0-base-ubuntu22.04)	3m 15s
build (nvidia/cuda:11.8.0-base-ubuntu20.04)	3m 52s
build (nvidia/cuda:11.7.1-base-ubuntu22.04)	3m 11s
build (nvidia/cuda:11.7.1-base-ubuntu20.04)	3m 5s
build (nvidia/cuda:11.6.2-base-ubuntu20.04)	3m 21s
build (nvidia/cuda:11.4.3-base-ubuntu20.04)	4m 1s
build (nvidia/cuda:11.3.1-base-ubuntu20.04)	3m 29s
build (nvidia/cuda:11.2.2-base-ubuntu20.04)	3m 7s
release	4s
	1h 12m 32s

Provide feedback