[hotfix] Add the missing ',' for HybridSnapshotLogSplit#toString()

Author: swuferhong

fluss-flink/fluss-flink-common/src/main/java/org/apache/fluss/flink/source/split/HybridSnapshotLogSplit.java

@@ -99,7 +99,7 @@ public String toString() {
                 + partitionName
                 + "', snapshotId="
                 + snapshotId
-                + "isSnapshotFinished="
+                + ", isSnapshotFinished="
                 + isSnapshotFinished
                 + ", logStartingOffset="
                 + logStartingOffset