Update content/manuals/engine/security/rootless/troubleshoot.md

Co-authored-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

Author: AkihiroSuda

content/manuals/engine/security/rootless/troubleshoot.md

@@ -301,7 +301,8 @@ The TCP/IP stack in user mode is generally slower than the one in kernel mode, a
 See [RootlessKit documentation](https://github.com/rootless-containers/rootlesskit/blob/v3.0.0/docs/network.md)
 for more information.
 
-**Workaround 1**
+##### Workaround 1: bypass user-mode TCP/IP stack
+
 Use `docker run --net=host` to bypass the user-mode TCP/IP stack.
 This is applicable since Docker Engine v29.5.
 However, this requires the container to share the host network namespace, which may not be desirable for security reasons.