`cpython` and `cpython_sym` look like the same labels in integration_tests

[ubaidsk]

https://github.com/lcompilers/lpython/blob/dfeacbc07fc6cfc837d95b848dcb6370a5876190/integration_tests/CMakeLists.txt#L216

It seems cpython and cpython_sym labels in the integration_tests/CMakelists.txt are similar (or even same). In that case, I think we can remove cpython_sym and simply reuse cpython for simplicity.