fix: remove duplicate code left by main-merge auto-resolution

The merge of main into pr-a-incremental-cleanup auto-resolved by
keeping both copies in two places:
  * transaction.cc: a duplicate Result<const TableMetadata*>
    finalize_result definition, which made the file fail to compile.
  * expire_snapshots.cc: an orphaned ReachableFileCleanup direct call
    plus the obsolete TODO comment after the now-correct dispatch
    inside Finalize(), which made clang-format fail in CI.

Drop the duplicates so the file compiles and matches the intended
post-merge state.

Author: shangxinli

src/iceberg/transaction.cc

@@ -368,11 +368,6 @@ Result<std::shared_ptr<Table>> Transaction::Commit() {
           ? Result<const TableMetadata*>(commit_result.value()->metadata().get())
           : std::unexpected(commit_result.error());
 
-  Result<const TableMetadata*> finalize_result =
-      commit_result.has_value()
-          ? Result<const TableMetadata*>(commit_result.value()->metadata().get())
-          : std::unexpected(commit_result.error());
-
   for (const auto& update : pending_updates_) {
     std::ignore = update->Finalize(finalize_result);
   }

src/iceberg/update/expire_snapshots.cc

@@ -929,11 +929,4 @@ Status ExpireSnapshots::Finalize(Result<const TableMetadata*> commit_result) {
                               expired_ids, cleanup_level_);
 }
 
-  ReachableFileCleanup strategy(ctx_->table->io(), delete_func_);
-  return strategy.CleanFiles(metadata_before_expiration, metadata_after_expiration,
-                             expired_ids, cleanup_level_);
-}
-
-// TODO(shangxinli): add IncrementalFileCleanup strategy for linear ancestry optimization.
-
 }  // namespace iceberg