Remove instrumentation for `koa-router`

[bizob2828]

Description

koa-router has been deprecated for 6 years. They are directing people to use @koa/router. We have instrumentation for koa-router and @koa/router as well as tests. We should remove support for the deprecated package and clean up the shared versioned tests.

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-497162