build fix

Author: Innocent

src/iceberg/metrics/json_serde.cc

@@ -68,7 +68,6 @@ constexpr std::string_view kPositionalDeleteFiles = "positional-delete-files";
 constexpr std::string_view kDvs = "dvs";
 
 // CommitMetricsResult keys
-constexpr std::string_view kTotalDuration = "total-duration";
 constexpr std::string_view kAttempts = "attempts";
 constexpr std::string_view kAddedDataFiles = "added-data-files";
 constexpr std::string_view kRemovedDataFiles = "removed-data-files";