fix: remove flake8 from make qa (PR feedback)

Author: yt-ms

Makefile

@@ -8,7 +8,6 @@
 qa:
 	isort src/structurizr/ tests/ examples/ setup.py
 	black src/structurizr/ tests/ examples/ setup.py
-	flake8 src/structurizr/ tests/ examples/ setup.py
 
 ## Prepare a release by generating the automatic code documentation.
 release: