Remove dead support for Java Service Wrapper

This commit removes bootstrap support for Java Service Wrapper. The
implementation of this has been moved to its own repository where it was
deprecated, does not work with Elasticsearch 2.x, and is untested and
therefore unmaintained.

Closes #16580

core/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -254,10 +254,6 @@ final class Bootstrap {
         INSTANCE = new Bootstrap();
 
         boolean foreground = !"false".equals(System.getProperty("es.foreground", System.getProperty("es-foreground")));
-        // handle the wrapper system property, if its a service, don't run as a service
-        if (System.getProperty("wrapper.service", "XXX").equalsIgnoreCase("true")) {
-            foreground = false;
-        }
 
         Environment environment = initialSettings(foreground);
         Settings settings = environment.settings();