Settings: Fix typo in defaults.ini (#17707)

`backround` -> `backGround`

conf/defaults.ini

@@ -394,7 +394,7 @@ enabled = false
 config_file = /etc/grafana/ldap.toml
 allow_sign_up = true
 
-# LDAP backround sync (Enterprise only)
+# LDAP background sync (Enterprise only)
 sync_cron = @hourly
 active_sync_enabled = false