fix(koolbox): Address krew with absolute path

For a reason I haven't fully figured out yet, the kubectl plugin
discovery in kaniko doesn't work like in podman or docker. This is
probably due to how they invoke shells for the container build. Either
way, this adjustment should hopefully fix it.

images/koolbox/.release

-release=0.4.0
+release=0.4.1

images/koolbox/Dockerfile

@@ -190,9 +190,9 @@ RUN true \
     && true
 
 RUN true \
-   && /usr/local/bin/kubectl krew install cyclonus \
-   && /usr/local/bin/kubectl krew install outdated \
-   && /usr/local/bin/kubectl krew install access-matrix \
+   && /usr/local/bin/kubectl-krew install cyclonus \
+   && /usr/local/bin/kubectl-krew install outdated \
+   && /usr/local/bin/kubectl-krew install access-matrix \
    && true
 
 # Create workspace