wrk: improve test.

`-d 1` makes `wrk` only run for 1 second, which is the least amount of time. The default is 10 seconds. And we'll hit `example.com` instead of GitHub since example.com fronted by a CDN and whatnot.
wrk: add 3.1.0 bottle.

Closes #30966.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>