Upgrade docbook-reference-plugin to 0.2.6

build.gradle

@@ -4,7 +4,7 @@ buildscript {
 	}
 	dependencies {
 		classpath("org.springframework.build.gradle:propdeps-plugin:0.0.3")
-		classpath("org.springframework.build.gradle:docbook-reference-plugin:0.2.4")
+		classpath("org.springframework.build.gradle:docbook-reference-plugin:0.2.6")
 	}
 }