[chore](cloud) enable fdb 7.3.69 by default (#60419)

Author: w41ter

cloud/src/common/config.h

@@ -33,7 +33,7 @@ CONF_String(fdb_cluster_file_path, "./conf/fdb.cluster");
 CONF_Bool(enable_fdb_external_client_directory, "true");
 // The directory path of external foundationdb client library.
 // eg: /path/to/dir1:/path/to/dir2:...
-CONF_String(fdb_external_client_directory, "");
+CONF_String(fdb_external_client_directory, "./lib/fdb/7.3.69/");
 CONF_String(http_token, "greedisgood9999");
 // use volatile mem kv for test. MUST NOT be `true` in production environment.
 CONF_Bool(use_mem_kv, "false");