testsuite: remove xfail flifetime-dse[24].C

	The testcases no longer are failing due to operator new, so
remove the xfails to reduce testsuite summary noise.

gcc/testsuite/ChangeLog:

2020-08-11  David Edelsohn  <dje.gcc@gmail.com>

	* g++.dg/opt/flifetime-dse2.C: Remove AIX xfail.
	* g++.dg/opt/flifetime-dse4.C: Remove AIX xfail.