Revert "Use SELinux mount flag for secrets"

This reverts commit 874192568f.

podman_compose.py

@@ -578,7 +578,7 @@ def get_secret_args(compose, cnt, secret):
         source_file = os.path.realpath(
             os.path.join(basedir, os.path.expanduser(source_file))
         )
-        volume_ref = ["--volume", f"{source_file}:{dest_file}:z,ro,rprivate,rbind"]
+        volume_ref = ["--volume", f"{source_file}:{dest_file}:ro,rprivate,rbind"]
         if uid or gid or mode:
             sec = target if target else secret_name
             log(