docs : change customCheProperties to extraProperties (#2597)

modules/administration-guide/partials/con_understanding-che-server-advanced-configuration.adoc

@@ -13,7 +13,7 @@ Advanced configuration is necessary to:
 * Override the properties automatically generated by the Operator from the standard `CheCluster` Custom Resource fields.
 
 
-The `customCheProperties` field, part of the `CheCluster` Custom Resource `server` settings, contains a
+The `extraProperties` field, part of the `CheCluster` Custom Resource `server` settings, contains a
 map of additional environment variables to apply to the {prod-short} server component.
 
 .Override the default memory limit for workspaces
@@ -34,7 +34,7 @@ spec:
 
 [NOTE]
 ====
-Previous versions of the {prod-short} Operator had a ConfigMap named `custom` to fulfill this role. If the {prod-short} Operator finds a `configMap` with the name `custom`, it adds the data it contains into the `customCheProperties` field, redeploys {prod-short}, and deletes the `custom` `configMap`.
+Previous versions of the {prod-short} Operator had a ConfigMap named `custom` to fulfill this role. If the {prod-short} Operator finds a `configMap` with the name `custom`, it adds the data it contains into the `extraProperties` field, redeploys {prod-short}, and deletes the `custom` `configMap`.
 ====
 
 .Additional resources