Bump Docker Buildx from 0.7.1 to 0.8.2
Bump Docker Buildx from 0.7.1 to 0.8.2

0.8.0 release notes: https://github.com/docker/buildx/releases/tag/v0.8.0
0.8.1 release notes: https://github.com/docker/buildx/releases/tag/v0.8.1
0.8.2 release notes: https://github.com/docker/buildx/releases/tag/v0.8.2

buildkite/elastic-ci-stack-for-aws