Docs: Fix expressions enabled description (#30589)

conf/defaults.ini

@@ -895,5 +895,5 @@ use_browser_locale = false
 default_timezone = browser
 
 [expressions]
-# Disable expressions & UI features
+# Enable or disable the expressions functionality.
 enabled = true

conf/sample.ini

@@ -885,5 +885,5 @@
 ;default_timezone = browser
 
 [expressions]
-# Disable expressions & UI features
+# Enable or disable the expressions functionality.
 ;enabled = true

docs/sources/administration/configuration.md

@@ -1515,6 +1515,6 @@ Set this to `true` to have date formats automatically derived from your browser
 Used as the default time zone for user preferences. Can be either `browser` for the browser local time zone or a time zone name from the IANA Time Zone database, such as `UTC` or `Europe/Amsterdam`.
 
 ## [expressions]
->Note: This is available in Grafana v7.4 and later versions.
+> **Note:** This feature is available in Grafana v7.4 and later versions.
 ### enabled
 Set this to `false` to disable expressions and hide them in the Grafana UI. Default is `true`.