Upgrade to Couchbase Cache Client 2.1.0

As of 2.1 cache expiration times are to be set in seconds. This commit
migrates to the new method, yet keeping the milliseconds unit.

Closes gh-7824

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -4094,7 +4094,7 @@ cache:
 		public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() {
 			return c -> {
 				c.prepareCache("biz", CacheBuilder.newInstance(anotherBucket())
-						.withExpirationInMillis(2000));
+						.withExpiration(2));
 			};
 		}