Remove Echo-specific references from extractor files

Keep extrator.go and extrator_test.go free of Echo-specific mentions
so they can be copied for use outside of Echo. The Echo-specific
scenarios remain covered in otel_test.go.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: suzuki-safie

extrator.go

@@ -561,7 +561,7 @@ func SpanNameFormatter(v Values) string {
 }
 
 // SpanStatus returns the span status code and error description for a server span, based on the
-// resolved HTTP status code (see [echo.ResolveResponseStatus]) and the error returned from the handler.
+// resolved HTTP response status code and the error that occurred while handling the request.
 //
 // Spec:
 //
@@ -587,8 +587,8 @@ func SpanStatus(code int, err error) (codes.Code, string) {
 	}
 	if code >= 400 {
 		// this instrumentation creates server spans, and for those the convention is to leave
-		// the status unset on 4xx responses, even when the handler returned an error that
-		// resolves to 4xx (e.g. echo.NewHTTPError(400)).
+		// the status unset on 4xx responses, even when the error is what the status code was
+		// resolved from.
 		return codes.Unset, ""
 	}
 	if err != nil { // an error alongside a 1xx-3xx status indicates another error occurred

extrator_test.go

@@ -6,7 +6,6 @@ import (
 	"net/http"
 	"testing"
 
-	"github.com/labstack/echo/v5"
 	"github.com/stretchr/testify/assert"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
@@ -752,9 +751,9 @@ func TestSpanStatus(t *testing.T) {
 			expectDesc: "",
 		},
 		{
-			name:       "client error 400 with handler error is left unset for server span",
+			name:       "client error 400 with error is left unset for server span",
 			whenStatus: 400,
-			whenError:  echo.NewHTTPError(http.StatusBadRequest, "invalid request"),
+			whenError:  errors.New("invalid request"),
 			expectCode: codes.Unset,
 			expectDesc: "",
 		},