fix: remove spurious double blank line in handleEnroll_test.go on 9.5 backport

Conflict resolution left two consecutive blank lines before
TestValidateEnrollRequest; mage check:fix requires a single blank line.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ycombinator

internal/pkg/api/handleEnroll_test.go

@@ -654,7 +654,6 @@ func TestCreateFleetAgentSyncWriteErrorSurfaces(t *testing.T) {
 	require.Error(t, err)
 }
 
-
 func TestValidateEnrollRequest(t *testing.T) {
 	t.Run("invalid json", func(t *testing.T) {
 		req, err := validateRequest(context.Background(), strings.NewReader("not a json"))