Revert back to `coverage==5.2`.
Revert back to `coverage==5.2`.

The newer versions were causing the CI test runs to consume all of the
memory, and running out of it.

Fixes https://github.com/saltstack/salt/issues/62989

Signed-off-by: Pedro Algarvio <09cbe6caca393bd5bff64d4c1f1ad660b906a807@vmware.com>

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt