Add closing backtick to fix missing placeholder

Without the closing backtick, <CountryOrRegion> was interpreted as a (disallowed) HTML tag, and the placeholder did not appear in the published page.

Author: garycentric

exchange/exchange-ps/exchange/Set-OrganizationConfig.md

@@ -1512,7 +1512,7 @@ You can use the following user attributes. The actual values are determined by t
 - `<City>`
 - `<Company>`
 - `<CountryCode>`
-- `<CountryOrRegion>
+- `<CountryOrRegion>`
 - `<CustomAttribute1>` to `<CustomAttribute15>`
 - `<Department>`
 - `<ExtensionCustomAttribute1>` to `<ExtensionCustomAttribute5>`