Add a comment in TEST_MAPPING that ath_config has to be updated

Bug: N/A
Test: N/A
Change-Id: Ibcbe61aed181cfed098e1b0f9d9be3a14c6fd63a
diff --git a/libs/capabilities/TEST_MAPPING b/libs/capabilities/TEST_MAPPING
index 568a771..902c6e5 100644
--- a/libs/capabilities/TEST_MAPPING
+++ b/libs/capabilities/TEST_MAPPING
@@ -1,3 +1,5 @@
+// When adding or removing tests here, don't forget to amend _all_modules list in
+// wireless/android/busytown/ath_config/configs/prod/avf/tests.gcl
 {
   "avf-presubmit" : [
     {