gh-actions: add flake8-no-print to flake8 lint step

Author: mofosyne

.github/workflows/python-lint.yml

@@ -22,3 +22,4 @@ jobs:
         with:
             ignore: "E203,E211,E221,E225,E231,E241,E251,E261,E266,E501,E701,E704,W503"
             exclude: "examples/*,examples/*/**,*/**/__init__.py"
+            plugins: "flake8-no-print"