bugfix: Bump pytest-operator to 0.31.1

Updating integration test dependency resolves error with pytest async plugin.

Signed-off-by: Jason C. Nucciarone <[email protected]>

tox.ini

@@ -60,7 +60,7 @@ description = Run integration tests
 deps =
     juju
     pytest==7.2.0
-    pytest-operator==0.26.0
+    pytest-operator==0.31.1
     pytest-order==1.1.0
     tenacity==8.2.2
     -r{toxinidir}/requirements.txt