zshでhomebrewで入れたaws-cli-v2の補完を効かせる

https://docs.aws.amazon.com/ja_jp/cli/latest/userguide/cli-configure-completion.html

# AWS CLI v2
autoload bashcompinit && bashcompinit
autoload -Uz compinit && compinit
compinit
complete -C aws_completer aws