Fix: Rubocop prevent multi except tests

[malparty]

Issue

While our conventions preffer single-expectation tests, it is also clear that some integration tests should use multiple expectations in order to maintain good performances.

Expected

Rubocop should not make the codebase tests fail if we are using multiple expectations in our codebase.

Steps to reproduce

1. Generate a new Rails app
2. Add a system test with 2 expects.
3. Run all the tests. The codebase tests will fail.