fix: small typo for transaction test (#1341)

## Which issue does this PR close?



N/A

## What changes are included in this PR?



Tiny typo fix I noticed whilst digging around this transaction code.

## Are these changes tested?



N/A, this fixes a small comment.

Author: jdockerty

crates/iceberg/src/transaction/append.rs

@@ -293,7 +293,7 @@ mod tests {
             new_snapshot.sequence_number()
         );
 
-        // check manifset
+        // check manifest
         let manifest = manifest_list.entries()[0]
             .load_manifest(table.file_io())
             .await