[CIR] Fix failing lit test (statement-exprs.c) (llvm#167000)

This fixes a test case in the clang/CIR/CodeGen/statement-exprs.c test.
The test case was copied from a similar test in clang/CodeGen/exprs.c
and was recently broken by
llvm#166036 which corrects Clang's
behavior with trailing NullStmts. This change updates the CIR test in
the same way that the classic codegen test was updated, removing the
trailing null part of the expression.

Author: andykaylor