[fix][client] Fix memory leak in ClientCnx.newLookup when there's Too…

…ManyRequestsException (apache#23971)

(cherry picked from commit 9d767b3)

pulsar-client/src/main/java/org/apache/pulsar/client/impl/ClientCnx.java

@@ -859,6 +859,7 @@ public CompletableFuture<LookupDataResult> newLookup(ByteBuf request, long reque
             if (maxLookupRequestSemaphore.tryAcquire()) {
                 waitingLookupRequests.add(Pair.of(requestId, Pair.of(request, future)));
             } else {
+                request.release();
                 if (log.isDebugEnabled()) {
                     log.debug("{} Failed to add lookup-request into waiting queue", requestId);
                 }