MINOR: Remove OffsetsForLeaderEpochRequest unused static field (apache#20418)

This field was used for replica_id, but after

apache@51c833e,
the OffsetsForLeaderEpochRequest directly relies on the internal structs
generated by the automated protocol. Therefore, we can safely remove it.

Reviewers: Lan Ding <[email protected]>, TengYao Chi
<[email protected]>

Author: m1a2st

clients/src/main/java/org/apache/kafka/common/requests/OffsetsForLeaderEpochRequest.java

@@ -36,12 +36,6 @@ public class OffsetsForLeaderEpochRequest extends AbstractRequest {
      */
     public static final int CONSUMER_REPLICA_ID = -1;
 
-    /**
-     * Sentinel replica_id which indicates either a debug consumer or a replica which is using
-     * an old version of the protocol.
-     */
-    public static final int DEBUGGING_REPLICA_ID = -2;
-
     private final OffsetForLeaderEpochRequestData data;
 
     public static class Builder extends AbstractRequest.Builder<OffsetsForLeaderEpochRequest> {