Remove http.route from http span attributes

[dyladan]

It seems to me we should actually not be setting the route parameter.

Originally posted by @dyladan in #2487 (comment)

According to the spec, the http.route parameter should be the low-cardinality template route like /user/:id. In the http instrumentation, we don't have access to that information and we populate the whole route like /user/123 but that information is already available in the http.target attribute.

[vmarchaud]

Note that we override it if another instrumentation (for http frameworks) has given the low cardinality route https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-instrumentation-http/src/utils.ts#L494

[dyladan]

that's fine but if you're not using one of those instrumentations then it's a duplicated field (with http.target) so there's no reason to have it.

[mustafain117]

@dyladan I can work on this, please assign this to me.