fix: use rustls-tls as native-tls-vendored doesn't work in a container

[shariqnaiyer]

What was wrong?

Fixes:

thread 'tokio-runtime-worker' (8) panicked at bin/ream/src/main.rs:235:14:
Failed to fetch checkpoint state: error sending request for url (https://leanpoint.leanroadmap.org/lean/v0/states/finalized)

Caused by:
    0: client error (Connect)
    1: error:0A000086:SSL routines:tls_post_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:2123: (unable to get local issuer certificate)
    2: error:0A000086:SSL routines:tls_post_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:2123:
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
2026-02-20T17:52:51.073453Z  INFO ream: Service exited, shutting down...
2026-02-20T17:52:51.073508Z  WARN ream_executor: Failed to send shutdown signal: channel closed

How was it fixed?

We now get the following which is what we expect.

thread 'tokio-runtime-worker' panicked at bin/ream/src/main.rs:235:14:                                                                                                
Failed to fetch checkpoint state: HTTP error 503 Service Unavailable: stale  

To-Do

• I have read CONTRIBUTING.md.
• This PR title follows conventional commits.

[KolbyML]

looks good