[polish] Add type parameter for MySqlRecords(#2300)

(cherry picked from commit bca60a4)

Author: TyrantLucifer

flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/split/MySqlRecords.java

@@ -36,7 +36,7 @@ public final class MySqlRecords implements RecordsWithSplitIds<SourceRecords> {
 
     public MySqlRecords(
             @Nullable String splitId,
-            @Nullable Iterator recordsForSplit,
+            @Nullable Iterator<SourceRecords> recordsForSplit,
             Set<String> finishedSnapshotSplits) {
         this.splitId = splitId;
         this.recordsForSplit = recordsForSplit;