Drop 3.6 (#207)

GitHub is raggedly allowing 3.5 and 3.6 support in Linux to drop from
the `setup-python` action as they start using Ubuntu 22.04 instead of
20.04. actions/setup-python#544

Example failure at
https://github.com/python-qt-tools/PyQt5-stubs/actions/runs/3645895301/jobs/6156457796#step:3:9.

```
Version 3.6.0-alpha - 3.6.X was not found in the local cache
Error: Version 3.6.0-alpha - 3.6.X with arch x64 not found
The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json
```

We could also just make our matrix ragged as well and only drop the
Linux testing. Or, explicitly call out the 20.04 runners for awhile. Let
me know what you think.

Author: altendky

.github/workflows/ci.yml

@@ -36,9 +36,6 @@ jobs:
             runs-on: windows-latest
             tox: windows
         python:
-          - name: CPython 3.6
-            tox: py36
-            action: 3.6
           - name: CPython 3.7
             tox: py37
             action: 3.7

setup.py

@@ -47,7 +47,7 @@ def find_version(*file_paths):
     long_description=long_description,
     long_description_content_type="text/markdown",
     version=find_version('PyQt5-stubs', '__init__.pyi'),
-    python_requires=">= 3.5",
+    python_requires=">= 3.7",
     package_data={"PyQt5-stubs": ['*.pyi']},
     packages=["PyQt5-stubs"],
     extras_require={

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py3{6,7,8,9,10}-{windows,linux}
+envlist = py3{7,8,9,10}-{windows,linux}
 
 [testenv]
 deps =