fix: require Python >= 3.10

pyproject.toml declared requires-python >= 3.9, but the codebase uses
annotations that are incompatible with Python 3.9: builtin generic
tuple[str, str] in parse_date_range (cli.py) and PEP 604 unions
str | None (config.py, yaml_config.py), the latter requiring 3.10+
at runtime.

Bump requires-python to >=3.10 and drop the Python 3.9 classifier.

Closes #51

pyproject.toml

@@ -11,13 +11,12 @@ authors = [{ name = "Artem Kokos", email = "artem-kokos@mail.ru" }]
 license = { text = "MIT" }
 classifiers = [
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Operating System :: POSIX :: Linux",
     "Environment :: Console",
 ]
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 dependencies = [
     "python-redmine>=2.4.0",
     "tabulate>=0.9.0",