Deploy release 1.26 to prod

[davidmegginson]

• libhxl-python release 4.26 on PyPi (@davidmegginson)
• confirm all other issues closed or moved to a different milestone
• confirm all hxl-proxy unit tests pass
• update version to "1.26" in both setup.py and hxl_proxy/__init__.py
• update libhxl requirement in requirements.txt and setup.py to v.4.26
• confirm CHANGELOG up to date
• commit changes
• test in clean virtualenv
• test Docker build locally: $ sudo docker build --no-cache -t unocha/hxl-proxy:local .
• merge to git test branch and push
• merge to git main branch and push
• add git tag "1.26"
• create GitHub release 1.26
• create PyPi release: pip install twine && rm -rf dist/* && python setup.py sdist && twine upload dist/*
• wait for and verify the 1.26 build on ECR succeeds: https://gallery.ecr.aws/unocha/hxl-proxy
• deploy to staging
• test in staging using test links: $ cat tests/browser-tests/staging-urls.txt | xargs -d '\n' firefox (or for macos users: for url in $(cat tests/browser-tests/staging-urls.txt); do open $url; done )
• deploy to prod
• test in prod using test links: $ cat tests/browser-tests/prod-urls.txt | xargs -d '\n' firefox (or for macos users: for url in $(cat tests/browser-tests/prod-urls.txt); do open $url; done )