bindings: cxx: vix compile errors

bindings: cxx: vix compile errors

This fixes the following compile errors:
tests-event.cpp:152:3: error: cannot declare reference to
'class std::system_error&', which is not a typedef or a template type
argument
  152 |   REQUIRE_THROWS_AS(line.event_get_fd(), ::std::system_error&);

This occurs on catch2 but not on catch.

Signed-off-by: Alexander Stein <alexander.stein@mailbox.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>