Fix broken links in reference documentation #1647
Description
The two links below should likely point to snapshot instead of libs-snapshot
403 FORBIDDEN: https://repo.spring.io/ui/repos/tree/General/libs-snapshot/org/springframework/data/spring-data-couchbase 403 FORBIDDEN: https://repo.spring.io/ui/repos/tree/General/libs-milestone/org/springframework/data/spring-data-couchbase