Remove unused header

Author: constracktor

tests/hpx_main.cpp

@@ -2,15 +2,14 @@
  * @file
  * @author Alexander Van Craen
  * @author Marcel Breyer
+ * @author Alexander Strack
  * @copyright 2018-today The PLSSVM project - All Rights Reserved
  * @license This file is part of the PLSSVM project which is released under the MIT license.
  *          See the LICENSE.md file in the project root for full license information.
  *
  * @brief Contains the googletest main function. Sets the DeathTest to "threadsafe" execution instead of "fast".
  */
 
-#include "plssvm/environment.hpp"  // plssvm::environment::scope_guard
-
 #include "gtest/gtest.h"  // RUN_ALL_TESTS, ::testing::{InitGoogleTest, GTEST_FLAG},GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST definitions
 
 #include <cstdlib>  // std::atexit