test: removing unneeded/expensive COPY
test: removing unneeded/expensive COPY

Test added in https://github.com/containers/buildah/pull/4310 uses `COPY
. .` which is expensive and unneeded. Also in `podman` test due to
copying files directly from the currect context it hits a
system/environment limit. See https://api.cirrus-ci.com/v1/artifact/task/5960273050730496/html/bud-podman-fedora-36-root-host.log.html#t--00004

Hence remove this uneeded `COPY` and instead use a `RUN echo`.

Closes: https://github.com/containers/buildah/issues/4314

Signed-off-by: Aditya R <4f9683854fe0b71db89677d592545c6b565c2266@redhat.com>

TomSweeneyRedHat/buildah,nalind/buildah-1,nalind/buildah-1,nalind/buildah-1,TomSweeneyRedHat/buildah,TomSweeneyRedHat/buildah