[clang] Partially revert "Disable a few formatting options for test/"

The changes to "AlignTrailingComments" and "CommentPragmas" did not
result in what I expected (just leave the special comments alone).

Instead now the following:
  void test() {
    int i; // expected-error
           // expected-warning
  }

is formatted into:
  void test() {
    int i; // expected-error
    // expected-warning
  }

which is even worse.