MdeModulePkg/UefiBootManagerLib: remove superfluous TimerLib dependency

MdeModulePkg/UefiBootManagerLib: remove superfluous TimerLib dependency

In commit 3a039a567a5f ("MdeModulePkg/UefiBootManagerLib: Remove the
useless perf codes", 2018-02-12), the BmWriteBootToOsPerformanceData()
function was removed. No TimerLib API calls are left, thus remove the
TimerLib class dependency from "InternalBm.h" and "UefiBootManagerLib.inf"
as well.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>