Docs: Fixup deprecation for asciidoctor (#48018)

Asciidoctor sees `,` as the edge of parameters and chokes on one of our
deprecation warnings, rendering funny looking garbage. This wraps the
whole parameter in `"` which makes it look good. It *does* add `"`s
around the result in AsciiDoc, but we plan to migrate from AsciiDoc
"real soon now".

docs/management/dashboard_only_mode/index.asciidoc

@@ -2,7 +2,7 @@
 [[xpack-dashboard-only-mode]]
 == Dashboard-only mode
 
-deprecated[7.4.0, Using the `kibana_dashboard_only_user` role is deprecated. Use <<kibana-feature-privileges,feature privileges>> instead.]
+deprecated[7.4.0, "Using the `kibana_dashboard_only_user` role is deprecated. Use <<kibana-feature-privileges,feature privileges>> instead."]
 
 In dashboard-only mode, users have access to only the *Dashboard* app. 
 Users can view and filter the dashboards, but cannot create, edit, or delete