Remove unused package

internal/requesterror/requesterror.go

-package requesterror
-
-import (
-	"fmt"
-	"net/http"
-)
-
-// For errors that occur while handling an HTTP request it is often
-// relevant what the request was for. This helper lets us consistently
-// embed request metadata in the error message.
-func New(context string, r *http.Request, format string, a ...interface{}) error {
-	return fmt.Errorf("%s: %s %q: %s", context, r.Method, r.RequestURI, fmt.Sprintf(format, a...))
-}