Defguide link should not use {branch}

docs/Versions.asciidoc

@@ -12,7 +12,7 @@ release-state can be: released | prerelease | unreleased
 :release-state:   unreleased
 
 :ref:             https://www.elastic.co/guide/en/elasticsearch/reference/{branch}
-:defguide:        https://www.elastic.co/guide/en/elasticsearch/guide/{branch}
+:defguide:        https://www.elastic.co/guide/en/elasticsearch/guide/master
 :plugins:         https://www.elastic.co/guide/en/elasticsearch/plugins/{branch}
 :javaclient:      https://www.elastic.co/guide/en/elasticsearch/client/java-api/{branch}
 :xpack:           https://www.elastic.co/guide/en/x-pack/5.0