Fix mailing lists endpoint path

src/main/java/org/eclipsefoundation/mailing/resources/MailingListsResource.java

@@ -30,7 +30,7 @@ import org.jboss.resteasy.specimpl.MultivaluedMapImpl;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-@Path("/mailing-list")
+@Path("/mailing_lists")
 @Produces(MediaType.APPLICATION_JSON)
 public class MailingListsResource {
     private static final Logger LOGGER = LoggerFactory.getLogger(MailingListsResource.class);