fix(test): drop unused fiber import

Three failed pushes in a row reminds the discipline: when modifying
the file, re-run go build before each push. Locally verified green
this time before push.

Author: mastermanas805

internal/middleware/optional_auth_strict_invalid_claims_test.go

@@ -17,7 +17,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/gofiber/fiber/v2"
 	jwt "github.com/golang-jwt/jwt/v4"
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"