chore(deps): update dependency gitlab-org/ci-cd/docker-machine to v0.16.2-gitlab.15-rc2

Author: renovate-bot

gitlab-runner.Dockerfile

@@ -18,7 +18,7 @@ RUN apk add --no-cache git
 WORKDIR /go/src/github.com/docker/machine
 
 # renovate: datasource=gitlab-tags depName=gitlab-org/ci-cd/docker-machine versioning=semver
-ARG DOCKER_MACHINE_VERSION=v0.16.2-gitlab.21
+ARG DOCKER_MACHINE_VERSION=v0.16.2-gitlab.15-rc2
 
 RUN git clone --branch=${DOCKER_MACHINE_VERSION}  https://gitlab.com/gitlab-org/ci-cd/docker-machine .
 RUN CGO_ENABLED=0 GO111MODULE=off go build -o docker-machine -trimpath -ldflags="-s -w" ./cmd/docker-machine