Reinstate LaunchedURLClassLoader's registration as parallel capable

Closes gh-7334

Author: dreis2211

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/LaunchedURLClassLoader.java

@@ -37,6 +37,10 @@
  */
 public class LaunchedURLClassLoader extends URLClassLoader {
 
+	static {
+		ClassLoader.registerAsParallelCapable();
+	}
+
 	/**
 	 * Create a new {@link LaunchedURLClassLoader} instance.
 	 * @param urls the URLs from which to load classes and resources