requirements[dev]: Upgrade mypy from ==0.961 to ~=1.0.0.

This is necessary since fresh environment builds (including CI) appear to pull
a version of types-requests that is broken with mypy < 1.0, types-requests
being the broken-out 3rd-party package of stubs for requests, but that is still
maintained in typeshed.

This appears to be python/typeshed#9702.

The mypy version is updated to ~=1.0.0 versioning now that it has moved to a
major/minor/point versioning scheme.

setup.py

@@ -51,7 +51,7 @@ def long_description():
 
 typing_deps = [
     "lxml-stubs",
-    "mypy==0.961",
+    "mypy~=1.0.0",
     "types-pygments",
     "types-python-dateutil",
     "types-tzlocal",