test/system: Remove redundant clean-up

The IMAGE_CACHE_DIR environment variable is defined as
"${BATS_SUITE_TMPDIR}/image-cache" [1].  Earlier, it used to be
"${BATS_RUN_TMPDIR}/image-cache".

There's no need to clean up anything inside BATS_RUN_TMPDIR or
BATS_SUITE_TMPDIR after the test suite has finished running, because
their life cycle is managed by Bats [2].

[1] Commit 3a549a6252
    https://github.com/containers/toolbox/commit/3a549a6252e990d6
    https://github.com/containers/toolbox/pull/1452

[2] https://bats-core.readthedocs.io/en/stable/writing-tests.html

Fallout from 9820550c82

https://github.com/containers/toolbox/pull/1645

test/system/libs/helpers.bash

@@ -120,12 +120,6 @@ function _pull_and_cache_distro_image() {
 }
 
 
-# Removes the folder with cached images
-function _clean_cached_images() {
-  rm --force --recursive "${IMAGE_CACHE_DIR}"
-}
-
-
 # Prepares a locally hosted image registry
 #
 # The registry is set up with Podman set to an alternative root. It won't

test/system/setup_suite.bash

@@ -1,6 +1,6 @@
 # shellcheck shell=bash
 #
-# Copyright © 2021 – 2024 Red Hat, Inc.
+# Copyright © 2021 – 2025 Red Hat, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -85,6 +85,5 @@ teardown_suite() {
     _clean_docker_registry
   fi
 
-  _clean_cached_images
   podman system reset --force >/dev/null
 }