pick-25 only-en fix guihint

Author: eseyffarth

src/onprem/en/upgrade.asciidoc

@@ -194,7 +194,7 @@ Of course, you can wait until all sites have been upgraded before restarting the
 {CMK} allows for xref:distributed_monitoring#mixed_editions[mixed operation] between a central site with a broader range of features, and remote sites with a more limited set of features.
 For the upgrade, this means that the central site receives the upgrade _first_.
 During mixed operation, the configuration should not be transferred from the central site to remote sites that have not yet received the upgrade.
-Therefore, we recommend disabling configuration changes on the central site via [.guihint]#Setup > General > Read-only mode# for the duration of mixed operation.
+Therefore, we recommend disabling configuration changes on the central site via [.guihint]#Setup > General > Read only mode# for the duration of mixed operation.
 Theoretically, such mixed operations can last indefinitely--in practice, however, configuration changes will become necessary after some time, requiring uniform editions across all sites.
 
 This results in the following processing sequence for the upgrade: