Tests: pin boto3

For https://github.com/boto/boto3/issues/4398

Also lint updates

Signed-off-by: Peter Sabaini <peter.sabaini@canonical.com>
Change-Id: Ieb248434b482f513060ca8b453e2068d51fde9cf

test-requirements.txt

@@ -30,3 +30,6 @@ git+https://opendev.org/openstack/tempest.git#egg=tempest
 
 croniter            # needed for charm-rabbitmq-server unit tests
 psutil
+
+# https://github.com/boto/boto3/issues/4392
+boto3<1.36.0

tox.ini

@@ -68,7 +68,7 @@ deps =
 basepython = python3
 deps =
     -c {env:TEST_CONSTRAINTS_FILE:https://raw.githubusercontent.com/openstack-charmers/zaza-openstack-tests/master/constraints/constraints-noble.txt}
-    flake8==3.9.2
+    flake8
     git+https://github.com/juju/charm-tools.git
 commands = flake8 {posargs} hooks unit_tests tests actions lib files
            charm-proof