Remove the SNCF bundle e2e test
The goal is to solve this issue:
With a previous PR (#828), I added two v15 e2e tests: Iris code submission and Iris result submission.
The test removed by this PR is testing "competition_15.zip" and "submission_15.zip", which is a template of SNCF competition. This bundle is not well rounded and documented, and the test seems to be randomly failing from time to time.
Maybe we want to really understand why this bundle creates problem. Or we can merge this PR and have stable tests from now on.