Remove override of the default route

[mcollina]

Signed-off-by: Matteo Collina hello@matteocollina.com

Just so you know, the change in the test is unrelated. That test checked if we trying to connect to a known route, and /echo/ was not registered, only /echo was.

Fixes #236.
Fixes platformatic/platformatic#575.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[airhorns]

Yeah, looking into it, I think that code was an attempt to keep support for a global websocket connection handler that this library used to support. Once this library started re-using fastify's router, that stopped being a thing though -- a route has to be matched before it can be upgraded. If users want one handler to process all incoming websocket connections, they should use a fastify.get("/*", {websocket: true}, ...), so I think this can be removed.