Undo fix for MDEV-13852: RocksDB now has a proper WinWriteableFile::IsSyncThreadSafe()

Commit being reverted is:
commit 689168be
Author: Vladislav Vaintroub <wlad@mariadb.com>
Date:   Thu Nov 16 18:57:18 2017 +0000

    MDEV-13852 - redefine WinWriteableFile such as IsSyncThreadSafe()
    is set to true, as it should.

    Copy and modify original io_win.h header file to a different location
    (as we cannot patch anything in submodule). Make sure modified header is
    used.

storage/rocksdb/build_rocksdb.cmake

@@ -12,11 +12,6 @@ INCLUDE_DIRECTORIES(
   ${ROCKSDB_SOURCE_DIR}/third-party/gtest-1.7.0/fused-src
 )
 
-IF(WIN32)
-  INCLUDE_DIRECTORIES(BEFORE
-  ${CMAKE_CURRENT_SOURCE_DIR}/patch)
-ENDIF()
-
 list(APPEND CMAKE_MODULE_PATH "${ROCKSDB_SOURCE_DIR}/cmake/modules/")
 
 if(WIN32)