fix: remove overload delay

@@ -17,28 +17,21 @@
 package com.google.cloud.spanner;
 
 import com.google.common.base.Preconditions;
-import org.threeten.bp.Duration;
-import org.threeten.bp.temporal.ChronoUnit;
 
 /**
 * Commit statistics are returned by a read/write transaction if specifically requested by passing
 * in {@link Options#commitStats()} to the transaction.
 */
 public class CommitStats {
 private final long mutationCount;
-private final Duration overloadDelay;
 
-private CommitStats(long mutationCount, Duration overloadDelay) {
+private CommitStats(long mutationCount) {
 this.mutationCount = mutationCount;
-this.overloadDelay = overloadDelay;
 }
 
 static CommitStats fromProto(com.google.spanner.v1.CommitResponse.CommitStats proto) {
 Preconditions.checkNotNull(proto);
-return new CommitStats(
-proto.getMutationCount(),
-Duration.of(proto.getOverloadDelay().getSeconds(), ChronoUnit.SECONDS)
-.plusNanos(proto.getOverloadDelay().getNanos()));
+return new CommitStats(proto.getMutationCount());
 }
 
 /**
@@ -58,9 +51,4 @@ static CommitStats fromProto(com.google.spanner.v1.CommitResponse.CommitStats pr
 public long getMutationCount() {
 return mutationCount;
 }
-
-/** The duration that the commit was delayed due to overloaded servers. */
-public Duration getOverloadDelay() {
-return overloadDelay;
-}
 }