[SR-5065] test/SILOptimizer/sil_combine_objc.sil is XFAIL'd

[dabrahams]

Previous ID	SR-5065
Radar	rdar://problem/32511494
Original Reporter	@dabrahams
Type	Bug

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | Bug | |Assignee | @gottesmm | |Priority | Medium | md5: 3924144609220201b140483bacce844a

Issue Description:

b2e4db5d09f XFAIL'd test/SILOptimizer/sil_combine_objc.sil because the test contained standard library dependencies for which I didn't know how to adjust. Sorry for the inconvenience.

[dabrahams]

@swift-ci create