Update flake8 requirement from <5.1,>=3.8 to >=3.8,<7.2 in /requireme…

…nts (#139)

requirements/development.txt

@@ -4,7 +4,7 @@
 -r base.txt
 
 black
-flake8>=3.8,<5.1
+flake8>=3.8,<7.2
 flake8-builtins>=1.5,<2.1
 flake8-isort>=4.0,<6.2
 isort>=5.7,<5.14