don't delete aizu downloaded tests on clean (#54)

Co-authored-by: Luke Videckis <lukevideckis@gmail.com>

Author: lrvideckis

.github/workflows/clean.sh

@@ -1,3 +1,3 @@
 #!/bin/bash
 cargo clean
-rm -rf default_*.profraw ptc_rust.profdata .verify-helper/
+rm -f default_*.profraw ptc_rust.profdata .verify-helper/timestamps.local.json