CI tests fail with aio-pika 6.8.2 (and above)

[ltalirz]

As can be seen from the PR #110 , the CI tests fail with later versions of aio-pika (e.g. version 8) due to API changes.

Furthermore, the Jupyter notebook test from the test suite seems to reproducibly fail with aio-pika version 6.8.2 but pass with aio-pika 6.8.1 (see commits in PR).

Until this is fixed, we may need to lock down the aio-pika version to ~6.6,<6.8.2