Restore use of avg in JPA smoke test

[snicoll]

While upgrading to Hibernate 6.2.0.Final, the smoke test has been changed to avoid what seems to be a regression in Hibernate 6.2. I've raised https://hibernate.atlassian.net/browse/HHH-16445 and the smoke test should be updated according to the resolution of that issue.

[dreis2211]

Meh, maybe this is a regression caused by https://hibernate.atlassian.net/browse/HHH-15711

[mhalbritter]

FTR, this is the commit which changed the avg: f264e3c

[wilkinsona]

I doesn't look like the regression's going to be fixed in Hibernate. There's a suggestion in the issue that we can use: casting to an integer.