**This Commit**
Updates the docs in the error handler middleware to match
[changes made to the website][website].
**Why?**
The previous documentation, when run, doesn't give the user a trivial
way to exercise the middleware because none of the routes return a
status code covered by the error handler middleware. There are also
additional routes that don't seem obviously instructive and so may
confuse a user into thinking error handlers only work with certain kinds
of requests.
[website]: https://github.com/actix/actix-website/pull/248
c00590497c