Docs: Fix caching.memcached setting name (#56606) (#56674)

(cherry picked from commit ef17f12c23)

Co-authored-by: Joan López de la Franca Beltran <5459617+joanlopez@users.noreply.github.com>

docs/sources/setup-grafana/configure-grafana/enterprise-configuration.md

@@ -474,7 +474,7 @@ The default is `"grafana"`.
 
 ## [caching.memcached]
 
-### memcached_servers
+### servers
 
 A space-separated list of memcached servers. Example: `memcached-server-1:11211 memcached-server-2:11212 memcached-server-3:11211`. Or if there's only one server: `memcached-server:11211`.