Restore max pool size limit in test

Author: marcphilipp

platform-tests/src/test/java/org/junit/platform/engine/support/hierarchical/ParallelExecutionIntegrationTests.java

@@ -267,7 +267,7 @@ void canRunTestsIsolatedFromEachOtherAcrossClassesWithOtherResourceLocks() {
 	void runsIsolatedTestsLastToMaximizeParallelism() {
 		var configParams = Map.of( //
 			DEFAULT_PARALLEL_EXECUTION_MODE, "concurrent", //
-			PARALLEL_CONFIG_FIXED_MAX_POOL_SIZE_PROPERTY_NAME, "4" //
+			PARALLEL_CONFIG_FIXED_MAX_POOL_SIZE_PROPERTY_NAME, "3" //
 		);
 		Class<?>[] testClasses = { IsolatedTestCase.class, SuccessfulParallelTestCase.class };
 		var events = executeWithFixedParallelism(3, configParams, testClasses) //