Release buffers in netty test (#126744)

Author: mhl-b

modules/transport-netty4/src/test/java/org/elasticsearch/http/netty4/Netty4HttpHeaderValidatorTests.java

@@ -111,7 +111,9 @@ public void testMixedValidationResults() {
             channel.writeInbound(last);
             if (shouldPassValidation) {
                 assertEquals("should pass content for valid request", content, channel.readInbound());
+                content.release();
                 assertEquals(last, channel.readInbound());
+                last.release();
             } else {
                 assertNull("should drop content for invalid request", channel.readInbound());
             }
@@ -138,7 +140,7 @@ public void testIgnoreReadWhenValidating() {
         assertNull("content should not pass yet, need explicit read", channel.readInbound());
 
         channel.read();
-        assertTrue(channel.readInbound() instanceof LastHttpContent);
+        asInstanceOf(LastHttpContent.class, channel.readInbound()).release();
     }
 
     public void testWithFlowControlAndAggregator() {
@@ -157,9 +159,8 @@ public void testWithFlowControlAndAggregator() {
         validationRequest.listener.onResponse(null);
         channel.runPendingTasks();
 
-        assertTrue(channel.readInbound() instanceof FullHttpRequest);
+        asInstanceOf(FullHttpRequest.class, channel.readInbound()).release();
     }
 
     record ValidationRequest(HttpRequest request, Channel channel, ActionListener<Void> listener) {}
-
 }