Explicitly prevent instantiation

(cherry picked from commit 940f24a)

Author: mrodbratschi

wrappercommon/src/main/java/com/genexus/diagnostics/core/provider/CustomMessageFactory.java

@@ -11,6 +11,7 @@
 @Plugin(name = "CustomMessageFactory", category = TemplateResolverFactory.CATEGORY)
 public final class CustomMessageFactory implements EventResolverFactory {
 	private static final CustomMessageFactory INSTANCE = new CustomMessageFactory();
+	private CustomMessageFactory() { /* no instances */ }
 
 	@PluginFactory
 	public static CustomMessageFactory getInstance() {