Update 7_1_release_notes.md (#49285)

* Update 7_1_release_notes.md

For context see #45867

Include in release notes the deprecation of `true` and `false` values
for `config.action_dispatch.show_exceptions` in favor of `:all`,
`:rescuable` and `:none`.

* Update 7_1_release_notes.md

Co-authored-by: Hartley McGuire <skipkayhil@gmail.com>

---------

Co-authored-by: Hartley McGuire <skipkayhil@gmail.com>
Co-authored-by: Rafael Mendonça França <rafael@rubyonrails.org>

guides/source/7_1_release_notes.md

@@ -492,12 +492,14 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 *   Deprecate `config.action_dispatch.return_only_request_media_type_on_content_type`.
 
-*   Deprecate `AbstractController::Helpers::MissingHelperError`
+*   Deprecate `AbstractController::Helpers::MissingHelperError`.
 
 *   Deprecate `ActionDispatch::IllegalStateError`.
 
 *   Deprecate `speaker`, `vibrate`, and `vr` permissions policy directives.
 
+*   Deprecate `true` and `false` values for `config.action_dispatch.show_exceptions` in favor of `:all`, `:rescuable`, or `:none`.
+
 ### Notable changes
 
 *   Add `exclude?` method to `ActionController::Parameters`. It is the inverse of `include?` method.