Remove unsupported values for config.action_dispatch.show_exceptions [ci skip]

Support for `true` and `false` was removed in
ec2c266.

Author: eugeneius

guides/source/configuring.md

@@ -2028,15 +2028,15 @@ defaults to `true`.
 
 The `config.action_dispatch.show_exceptions` configuration controls how Action Pack (specifically the [`ActionDispatch::ShowExceptions`](/configuring.html#actiondispatch-showexceptions) middleware) handles exceptions raised while responding to requests.
 
-Setting the value to `:all` or `true` configures Action Pack to rescue from exceptions and render corresponding error pages. For example, Action Pack would rescue from an `ActiveRecord::RecordNotFound` exception and render the contents of `public/404.html` with a `404 Not found` status code.
+Setting the value to `:all` configures Action Pack to rescue from exceptions and render corresponding error pages. For example, Action Pack would rescue from an `ActiveRecord::RecordNotFound` exception and render the contents of `public/404.html` with a `404 Not found` status code.
 
 Setting the value to `:rescueable` configures Action Pack rescue from exceptions defined in [`config.action_dispatch.rescue_responses`](/configuring.html#config-action-dispatch-rescue-responses), and raise all others. For example, Action Pack would rescue from `ActiveRecord::RecordNotFound`, but would raise a `NoMethodError`.
 
-Setting the value to `:none` or `false` configures Action Pack raise all exceptions.
+Setting the value to `:none` configures Action Pack raise all exceptions.
 
-* `:all`, `true` - render error pages for all exceptions
+* `:all` - render error pages for all exceptions
 * `:rescuable` - render error pages for exceptions declared by [`config.action_dispatch.rescue_responses`](/configuring.html#config-action-dispatch-rescue-responses)
-* `:none`, `false` - raise all exceptions
+* `:none` - raise all exceptions
 
 | Starting with version | The default value is  |
 | --------------------- | --------------------- |