increase timeout (Consensys#7891)

Signed-off-by: Paul Harris <[email protected]>

ethereum/spec/src/test/java/tech/pegasys/teku/spec/signatures/LocalSlashingProtectorConcurrentAccessTest.java

@@ -156,7 +156,8 @@ void canAccessDifferentValidatorConcurrently()
             });
     threadAcquired.await();
     assertThat(firstSigner).isNotCompleted();
-    secondSigner.get(50, TimeUnit.MILLISECONDS);
+    // flaky on Windows
+    secondSigner.get(500, TimeUnit.MILLISECONDS);
     assertThat(secondSigner).isCompleted();
     releaseLock.set(true);
     // flaky on Windows