[cxx-interop] Adjust an IRGen test for rebranch

This fixes `Interop/Cxx/class/returns-large-class-irgen.swift` by adjusting the expected function signature.

On rebranch, the actual signature is:
```
define void @_Z21funcReturnsLargeClassv(ptr dead_on_unwind noalias writable sret(%struct.LargeClass) align 8 %agg.result)
```

rdar://127263407

Author: egorzhdan

test/Interop/Cxx/class/returns-large-class-irgen.swift

@@ -17,4 +17,4 @@ foo()
 // CHECK: call swiftcc void @"$s4main3fooSo10LargeClassVyF"(ptr noalias nocapture sret(%TSo10LargeClassV) %{{.*}})
 
 // The C++ function:
-// CHECK: define{{( dso_local)?}} void @{{_Z21funcReturnsLargeClassv|"\?funcReturnsLargeClass@@YA\?AULargeClass@@XZ"}}({{%struct.LargeClass\*|ptr}} noalias sret(%struct.LargeClass){{( align .*)?}} %{{.*}})
+// CHECK: define{{( dso_local)?}} void @{{_Z21funcReturnsLargeClassv|"\?funcReturnsLargeClass@@YA\?AULargeClass@@XZ"}}({{%struct.LargeClass\*|ptr}}{{.*}} sret(%struct.LargeClass){{( align .*)?}} %{{.*}})