Add flask2.1 to CI runs (#495)

Author: vimalloc

.github/workflows/unit_tests.yml

@@ -22,3 +22,5 @@ jobs:
         run: pip install tox
       - name: Run Tox
         run: tox -e py
+      - name: Run Tox Flask==2.1
+        run: tox -e flask21

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py{37,38,39,310}-{flask21,flask},pypy3.9,mypy,coverage,style,docs
+envlist = py37,py38,py39,py310,pypy3.9,flask21,mypy,coverage,style,docs
 
 [testenv]
 commands =
@@ -14,7 +14,6 @@ deps =
   cryptography
   python-dateutil
   flask21: Flask>=2.1,<2.2
-  flask: Flask>=2.2
 
 [testenv:mypy]
 commands =