Fix test fail caused by proguard trimmed out reflection callback. am: 44c53a6729

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/Nearby/+/17046184

Change-Id: I750894ea0709273b7d473b8f4204d7e78cac44f2
diff --git a/nearby/tests/multidevices/clients/proguard.flags b/nearby/tests/multidevices/clients/proguard.flags
index ec8f526..2e34dce 100644
--- a/nearby/tests/multidevices/clients/proguard.flags
+++ b/nearby/tests/multidevices/clients/proguard.flags
@@ -3,6 +3,11 @@
      *;
 }
 
+# Keep simulator reflection callback.
+-keep class com.android.server.nearby.common.bluetooth.fastpair.testing.** {
+     *;
+}
+
 # Do not touch Mobly.
 -keep class com.google.android.mobly.** {
   *;