chore: reduce log verbosity when encountering non-standard files in _delta_log

kernel/src/listed_log_files.rs

@@ -21,7 +21,7 @@ use crate::{DeltaResult, Error, StorageHandler, Version};
 use delta_kernel_derive::internal_api;
 
 use itertools::Itertools;
-use tracing::{info, warn};
+use tracing::log::*;
 use url::Url;
 
 /// Represents the set of log files found during a listing operation in the Delta log directory.
@@ -286,7 +286,10 @@ impl ListedLogFiles {
                             }
                         }
                         Unknown => {
-                            warn!(
+                            // It is possible that there are other files being stashed away into
+                            // _delta_log/  This is not necessarily forbidden, but something we
+                            // want to know about in a debugging scenario
+                            debug!(
                                 "Found file {} with unknown file type {:?} at version {}",
                                 file.filename, file.file_type, version
                             );