Remove mock context class definition from device fixture

Signed-off-by: Mateusz Jablonski <mateusz.jablonski@intel.com>

level_zero/tools/test/unit_tests/sources/sysman/fabric_port/linux/mock_fabric_device.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2020 Intel Corporation
+ * Copyright (C) 2020-2022 Intel Corporation
  *
  * SPDX-License-Identifier: MIT
  *
@@ -8,6 +8,7 @@
 #pragma once
 #include "level_zero/core/test/unit_tests/fixtures/device_fixture.h"
 
+#include "gmock/gmock.h"
 #include "sysman/fabric_port/fabric_port.h"
 
 namespace L0 {