Update processing of config file in the test cases of optical throughput

Summary

Due to the new yaml configuration file, which will be loaded to calibpipe/doc/source/examples/throughput/configurations/, tests for optical throughput should be changed accordingly.

What is the expected correct behavior?

Tests for optical throughput should use new configurational file.

Possible fixes

Test scripts in calibpipe/calibpipe/tests/unittests/throughput should have changed path to config, its type and methods for processing it (from json to yaml).