Costools

Fixes error in S_REGION calculation
What's Changed
* S_REGION circle size should be RADIUS, not diameter by stscirij in https://github.com/spacetelescope/costools/pull/31


**Full Changelog**: https://github.com/spacetelescope/costools/compare/1.2.5...1.2.6

What's Changed
* Fix versions to current by stscirij in https://github.com/spacetelescope/costools/pull/27
* Add code to calculate COS S_REGION and put into keyword by stscirij in https://github.com/spacetelescope/costools/pull/26
* Upgrade checkout version to fix problem publishing to pypi by stscirij in https://github.com/spacetelescope/costools/pull/28
* Fix actions v2 by stscirij in https://github.com/spacetelescope/costools/pull/29
* Fix actions checkout version by stscirij in https://github.com/spacetelescope/costools/pull/30


**Full Changelog**: https://github.com/spacetelescope/costools/compare/1.2.4...1.2.5

Publicly release v1.2.3 that can be built with the Python 3.7 and Python 3.8 release tools.