Disable CPU overhead test due to flakyness (#2984)

Author: JonasKunz

apm-agent-core/src/test/java/co/elastic/apm/agent/metrics/builtin/AgentOverheadMetricsTest.java

@@ -27,6 +27,7 @@
 import co.elastic.apm.agent.util.ExecutorUtils;
 import com.sun.management.ThreadMXBean;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
@@ -69,6 +70,7 @@ public void setUp() {
  }
 
  @Test
+ @Disabled("due to flakyness")
  public void checkCpuMetrics() throws InterruptedException {
  //make sure that the OS provides a value for cpuLoad
  awaitNonZeroProcessCpuLoad();