generate-all-test-cases: don't wipe store

Afetr a run, a store contains downloaded rpm's and whatever pipelines
were checkpointed. We want to reuse these for subsequent runs, so
don't delet the store.
This risks minimally increasing the disk space usage, but should speed things up significantly.

tools/test-case-generators/generate-all-test-cases

@@ -705,8 +705,6 @@ class TestCaseMatrixGenerator(contextlib.AbstractContextManager):
                             log.info("Retrying image test case generation (%d of %d)", i, go_tls_timeout_retries)
 
                         stdout, stderr, retcode = runner.run_command(gen_test_cases_cmd)
-                        # clean up the osbuild-store dir
-                        runner.run_command_check_call(f"sudo rm -rf {guest_osbuild_store_dir}/*")
 
                         if retcode != 0:
                             log.error("'%s' retcode: %d\nstdout: %s\nstderr: %s", gen_test_cases_cmd, retcode,