Merge pull request #1162 from fluxcd/tidy-cmd-docs

cmd/flux/bootstrap_github.go

cmd/flux/bootstrap_gitlab.go

cmd/flux/check.go

cmd/flux/completion_bash.go

cmd/flux/completion_fish.go

cmd/flux/completion_powershell.go

cmd/flux/completion_zsh.go

cmd/flux/create_alert.go

cmd/flux/create_alertprovider.go

cmd/flux/create_helmrelease.go

cmd/flux/create_image.go

cmd/flux/create_image_policy.go

cmd/flux/create_image_repository.go

cmd/flux/create_image_update.go

cmd/flux/create_kustomization.go

cmd/flux/create_receiver.go

cmd/flux/create_secret_helm.go

cmd/flux/create_secret_tls.go

cmd/flux/create_source_bucket.go

cmd/flux/create_source_helm.go