Remove unused visibility spec (#2403)

BUG=cleanup

tensorflow/lite/micro/testing/BUILD

diff --git a/tensorflow/lite/micro/testing/BUILD b/tensorflow/lite/micro/testing/BUILD
index aad4a4c..11a52ad 100644
--- a/tensorflow/lite/micro/testing/BUILD
+++ b/tensorflow/lite/micro/testing/BUILD
@@ -33,7 +33,6 @@
     ],
     visibility = [
         ":kernel_test_friends",
-        ":microfrontend",
         ":tflite_micro",
     ],
     deps = [