test: catch include dir changed to catch2

For some reason catch had been renamed to catch2 a while ago, with v2.3.0 the include dir has also been changed.

https://github.com/catchorg/Catch2/releases/tag/v2.3.0

This means the path is now e.g. /usr/include/catch2 and in code you write #include <catch2/catch.hpp>