Remove duplicate definition of SimulationTime

- the "using SimulationTime=..." directive was moved to
Common/time_utils.h and renamed to "using Time=...". Please use this one
- SimulationTime was then redefined in Common/simulation_time.h as
"struct" to hold the simulation time (current&delta)

Signed-off-by: Andreas Rauschert <andreas.rb.rauschert@bmw.de>

MantleAPI/include/MantleAPI/Execution/simulation_time.h

-/*******************************************************************************
-* Copyright (c) 2021, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
-*
-* This program and the accompanying materials are made
-* available under the terms of the Eclipse Public License 2.0
-* which is available at https://www.eclipse.org/legal/epl-2.0/
-*
-* SPDX-License-Identifier: EPL-2.0
-*******************************************************************************/
-
-//-----------------------------------------------------------------------------
-/** @file  simulation_time.h */
-//-----------------------------------------------------------------------------
-
-
-#ifndef MANTLEAPI_EXECUTION_SIMULATIONTIME_H
-#define MANTLEAPI_EXECUTION_SIMULATIONTIME_H
-
-#include <chrono>
-#include <cstdint>
-
-namespace mantle_api
-{
-
-/// @brief Use milliseconds with std::int64_t representation as simulation time
-using SimulationTime = std::chrono::duration<std::int64_t, std::milli>;
-
-}  // namespace mantle_api
-
-#endif  // MANTLEAPI_EXECUTION_SIMULATIONTIME_H