japan: refactor japanese equinox holidays
Refactored japanese holidays to make use of Meeus algorithms
Include pymeeus in requirements_dev.txt which was already a
transitive dependency associated with convertdate
Sort dependencies alphabetically in requirements_dev.txt
# package runtime requirements
-python-dateutil
convertdate>=2.3.0
-korean_lunar_calendar
hijri_converter
+korean_lunar_calendar
+pymeeus
+python-dateutil
# test requirements
-pytest
-pytest-cov
coverage[toml]<7.0.0
-pre-commit
flake8
+pre-commit
+pytest
+pytest-cov
sphinx
tox
