refactor: downgrade stale _last_checkpoint log from warn! to info! (#777)

## What changes are proposed in this pull request?
Downgrade `warn!` to `info!` when `_last_checkpoint` is stale. Since
`_last_checkpoint` is only a hint and may frequently be out of date in a
busy system, logging it as a warning is unnecessary. Clients can still
see the info-level log if needed.

Co-authored-by: Zach Schuermann <zachary.zvs@gmail.com>

Author: sebastiantia

kernel/src/log_segment.rs

@@ -21,7 +21,7 @@ use crate::{
 use delta_kernel_derive::internal_api;
 
 use itertools::Itertools;
-use tracing::{debug, warn};
+use tracing::{debug, info, warn};
 use url::Url;
 
 #[cfg(test)]
@@ -741,7 +741,7 @@ fn list_log_files_with_checkpoint(
         ));
     };
     if latest_checkpoint.version != checkpoint_metadata.version {
-        warn!(
+        info!(
             "_last_checkpoint hint is out of date. _last_checkpoint version: {}. Using actual most recent: {}",
             checkpoint_metadata.version,
             latest_checkpoint.version