requirements[dev]: Upgrade mypy from ~=1.3.0 to ~=1.4.0.

Author: neiljp

setup.py

@@ -42,7 +42,7 @@ def long_description():
 
 typing_deps = [
     "lxml-stubs",
-    "mypy~=1.3.0",
+    "mypy~=1.4.0",
     "types-beautifulsoup4",
     "types-pygments",
     "types-python-dateutil",