[pstl] Remove our custom FindTBB CMake file

Summary:
The TBBConfig file installed by TBB 2019 Update 5 works properly, so we
don't need this workaround anymore.

Reviewers: rodgert, MikeDvorskiy

Subscribers: mgorny, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60467

llvm-svn: 358196

Author: ldionne

pstl/CMakeLists.txt

@@ -6,7 +6,6 @@
 #
 #===----------------------------------------------------------------------===##
 cmake_minimum_required(VERSION 3.4.3)
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
 set(PARALLELSTL_VERSION_FILE "${CMAKE_CURRENT_SOURCE_DIR}/include/pstl/internal/pstl_config.h")
 file(STRINGS "${PARALLELSTL_VERSION_FILE}" PARALLELSTL_VERSION_SOURCE REGEX "#define _PSTL_VERSION .*$")