Remove line numbers in ephy_testing_data/neuralynx/Cheetah_v5.6.3/plain_data

Two of the files in this part of the repository, CSC1.txt and CSC2.txt, have line numbers as the first column. This is different from the other similar plain_data files in the repository for other Cheetah versions and will cause the code in test_neuralynxio.TestData.test_ncs to fail on either this version or other versions when run over all the different versions. Presently the first line of test_ncs restricts itself to only the first two data directories, which has hidden this issue from the integration tests so far.

I have changes to the test code and the two files which fixes this, but it will require changing the test data in the annex of this repository. Unclear to me how to do that.

#22 Remove line numbers in ephy_testing_data/neuralynx/Cheetah_v5.6.3/plain_data