remove python 3.7 from CI

Signed-off-by: Tomasz Kłoczko <kloczek@github.com>

.github/workflows/tests.yml

@@ -17,7 +17,6 @@ jobs:
       matrix:
         config:
         # [Python version, tox env]
-        - ["3.7",   "py37"]
         - ["3.8",   "py38"]
         - ["3.9",   "py39"]
         - ["3.10",  "py310"]