test(backend): trim trailing blank lines in 1202 .ir snapshot (A7.1 scaffolding fix)

Codex review of d6078c2 flagged a blank line at EOF in the new
examples/expected/1202-ffi-cc-c-large-aggregate.ir. Collapse the trailing
newlines to a single one so `git diff --check` is clean. Test-safe: the runner
reads both expected and actual IR through $(...) command substitution, which
strips trailing newlines, so the comparison is unaffected (1202 still ok).

Gate: zig build, zig build test, bash tests/run_examples.sh -> 361/0.

examples/expected/1202-ffi-cc-c-large-aggregate.ir

@@ -178,5 +178,3 @@ entry:
   call void @CAllocator.dealloc(ptr %0, ptr %1, ptr %2)
   ret void
 }
-
-