Fixup test after changes made in 709fd989.

The change added a test that required exceptions, so enable that explicitly
so that it works on platforms that default to having exceptions disabled
(like the PS4).

clang-tools-extra/test/clang-tidy/checkers/modernize-use-default-member-init.cpp

@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy -std=c++11,c++14,c++17 %s modernize-use-default-member-init %t
+// RUN: %check_clang_tidy -std=c++11,c++14,c++17 %s modernize-use-default-member-init %t -- -- -fexceptions
 // FIXME: Fix the checker to work in C++2a mode.
 
 struct S {