[Support] Remove llvm/Support/Host.h (#74261)

The header file has been deprecated since:

  commit f09cf34d00625e57dea5317a3ac0412c07292148
  Author: Archibald Elliott <archibald.elliott@arm.com>
  Date:   Tue Dec 20 10:24:02 2022 +0000

GitOrigin-RevId: e1e34cc2a17c5f640333767df2d3bfe2b2f81a84
1 file changed