Remove node.max_local_storage_nodes from setup doc

Previously node.max_local_storage_nodes defaulted to fifty, and this
permitted users to start multiple instances of Elasticsearch sharing the
same data folder. This can be dangerous, and usually it does not make
sense to run more than one instance of Elasticsearch on a single
server. Because of this, we had a note in the important settings docs
advising users to set this setting to one. However, we have since
changed the default value of this setting to one so this advise is no
longer needed.

Relates #21305

docs/reference/setup/important-settings.asciidoc

@@ -188,29 +188,3 @@ be thrown which will prevent the node from starting.
 
 [float]
 [[node.max_local_storage_nodes]]
-=== `node.max_local_storage_nodes`
-
-It is possible to start more than one node on the same server from the same
-`$ES_HOME`, just by doing the following:
-
-[source,sh]
---------------------------------------------------
-./bin/elasticsearch -d
-./bin/elasticsearch -d
---------------------------------------------------
-
-This works just fine: the data directory structure is designed to let multiple
-nodes coexist.  However, a single instance of Elasticsearch is able to use all
-of the resources of a single server and it seldom makes sense to run multiple
-nodes on the same server in production.
-
-It is, however, possible to start more than one node on the same server by
-mistake and to be completely unaware that this problem exists. To prevent more
-than one node from sharing the same data directory, it is advisable to add the
-following setting:
-
-[source,yaml]
---------------------------------------------------
-node.max_local_storage_nodes: 1
---------------------------------------------------
-