remove kubectl installation from Dockerfile

kubectl doesn't seem to be in use anywhere within the code, so removing
it from the Dockerfile should simplify the image creation and shrink
the image size somewhat

Signed-off-by: Kevin <kpostlet@redhat.com>

Author: KPostOffice

Dockerfile

@@ -11,15 +11,13 @@ COPY pkg pkg
 COPY hack hack
 COPY CONTROLLER_VERSION CONTROLLER_VERSION
 
-RUN cd /workdir && curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/$(go env GOARCH)/kubectl && chmod +x kubectl
 ENV GO_BUILD_ARGS=$GO_BUILD_ARGS
 RUN echo "Go build args: $GO_BUILD_ARGS" && \
     make mcad-controller
 
 FROM registry.access.redhat.com/ubi8/ubi-minimal:latest
 
 COPY --from=BUILDER /workdir/_output/bin/mcad-controller /usr/local/bin
-COPY --from=BUILDER /workdir/kubectl /usr/local/bin
 
 RUN true \
     && microdnf update \