add grails4 tag

Author: sdelamo

gradle.properties

@@ -5,5 +5,5 @@ copyright=Copies of this document may be made for your own use and for distribut
 githubSlug=grails-guides/grails-test-security
 githubBranch=master
 category=Grails Testing
-tags=spring-security-rest,rest-api,functional-test,geb,spring-security-core,micronaut-http-client
+tags=spring-security-rest,rest-api,functional-test,geb,spring-security-core,micronaut-http-client,grails4
 publicationDate=16 Jan 2017