Express instrumentation uses `/` route for 404 routes

[mydea]

A span emitted for a 404 route (e.g. /does-not-exist) has the http.route attribute incorrectly set to /, which results in it being grouped & named incorrectly.

This needs to be fixed upstream in otel for v4 of express: open-telemetry/opentelemetry-js-contrib#1947

• Express v5
• Express v4: [instrumentation-express] http.route == "/" if every path matches open-telemetry/opentelemetry-js-contrib#1947