Drop upstream divergence in a test

This demonstrates the hazards of -NOT checks, this was checking
for no call to a function not called in the first place.

Author: arsenm

clang/test/CodeGenOpenCL/convergent.cl

@@ -65,7 +65,7 @@ void test_merge_if(int a) {
 // CHECK: br i1 %[[tobool]], label %[[if_end:.+]], label %[[if_then:.+]]
 // CHECK: [[if_then]]:
 // CHECK: tail call spir_func void @f()
-// CHECK-NOT: call spir_func void @non_convfun()
+// CHECK-NOT: call spir_func void @convfun()
 // CHECK-NOT: call spir_func void @g()
 // CHECK: br label %[[if_end]]
 // CHECK: [[if_end]]: