Variant got re-packaged, need to update search paths. (#3392)

include/server/service/base_service.hpp

@@ -5,7 +5,7 @@
 #include "osrm/osrm.hpp"
 #include "util/coordinate.hpp"
 
-#include <variant/variant.hpp>
+#include <mapbox/variant.hpp>
 
 #include <string>
 #include <vector>

include/util/json_container.hpp

@@ -31,7 +31,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef JSON_CONTAINER_HPP
 #define JSON_CONTAINER_HPP
 
-#include <variant/variant.hpp>
+#include <mapbox/variant.hpp>
 
 #include <string>
 #include <unordered_map>