Update gcr.io/pluralsh/plural-cli-cloud Docker tag to v0.5.21#256

plural-bot wants to merge 1 commit intomasterpluralsh/plural-cli:masterfrom

renovate/gcr.io-pluralsh-plural-cli-cloud-0.5.xpluralsh/plural-cli:renovate/gcr.io-pluralsh-plural-cli-cloud-0.5.xCopy head branch name to clipboard