drop SQLAlchemy 1.3, Python 3.8

drop SQLAlchemy 1.3, Python 3.8

Jenkins issues reveal that SQLAlchemy 1.3's testing provision has
unidentified deficiencies that are causing instability with the
mssql engine.   As provisioning was highly refactored in 1.4, just drop
1.3 support rather than trying to figure out the exact thing that
changed.

Support for SQLAlchemy 1.3, which was EOL as of 2021, is now dropped from
Alembic as of version 1.15.0.

Support for Python 3.8 is dropped as of Alembic 1.15.0.  Python 3.8 is EOL.

Try pytest 8.3 as this seems to be running fine for SQLAlchemy

Change-Id: I06614a6f73d5b1a1ac5b9b04225ecb305f5b35ee