Fix gzip not found issue on kanister-kubectl image (#1159)

In the recent release (`0.70.0`) of kanister we changed the
base image of kanister-tools image that resulted into a failure
in kanister-kubectl image.
It started failing with `gzip` command not found, and the reason
is when we run `microdnf update` on previous rh base image it
install gzip but not in the newere rh base image.
This commit install gzip manually.

docker/tools/Dockerfile

@@ -15,7 +15,7 @@ COPY --from=ghcr.io/kastenhq/kopia@sha256:ad987e7062686fb1c2485e7c1a942687086821
 COPY LICENSE /licenses/LICENSE
 
 ADD kando /usr/local/bin/
-RUN microdnf update && microdnf install shadow-utils httpd-tools && \
+RUN microdnf update && microdnf install shadow-utils httpd-tools gzip && \
   adduser -U kanister -u 1000 && \
   microdnf remove shadow-utils && \
   microdnf clean all