Fix broken includes in reference documentation.

Closes #1349

Author: schauder

src/main/asciidoc/index.adoc

@@ -4,7 +4,7 @@ Jens Schauder, Jay Bryant, Mark Paluch, Bastian Wilhelm
 :revdate: {localdate}
 :javadoc-base: https://docs.spring.io/spring-data/jdbc/docs/{revnumber}/api/
 ifdef::backend-epub3[:front-cover-image: image:epub-cover.png[Front Cover,1050,1600]]
-:spring-data-commons-docs: ../../../../../spring-data-commons/src/main/asciidoc
+:spring-data-commons-docs: ../../../../spring-data-commons/src/main/asciidoc
 :spring-framework-docs: https://docs.spring.io/spring-framework/docs/{springVersion}/reference/html
 :include-xml-namespaces: false