De-flake BluetoothLowEnergyWeave* tests.

components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc

Index: components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc
diff --git a/components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc b/components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc
index 26837fa0c852dcf0058251bdb88aafb00f5984b5..c376a794b606f015e47f5c78b7a7770077234e45 100644
--- a/components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc
+++ b/components/proximity_auth/ble/bluetooth_low_energy_weave_client_connection_unittest.cc
@@ -361,6 +361,13 @@ class ProximityAuthBluetoothLowEnergyWeaveClientConnectionTest
         receiver_factory_);
   }
 
+  ~ProximityAuthBluetoothLowEnergyWeaveClientConnectionTest() override {
+    BluetoothLowEnergyWeavePacketGenerator::Factory::SetInstanceForTesting(
+        nullptr);
+    BluetoothLowEnergyWeavePacketReceiver::Factory::SetInstanceForTesting(
+        nullptr);
+  }
+
   void SetUp() override {
     device_ = base::MakeUnique<NiceMock<device::MockBluetoothDevice>>(
         adapter_.get(), 0, kTestRemoteDeviceName,