Clean up GitHub Actions

[sseraj]

Purpose

Following up on #30 with some minor fixes for GHA:

1. Removed unused config files
2. Changed the default build and test script names to build.sh and test.sh. Most of our repos do not have separate real and complex tests so I think this makes more sense
3. Fixed some inconsistencies in the README

Expected time until merged

1-2 days

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run ruff check and ruff format to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[lamkina]

I think we can remove the build-bot and rtd directories during this cleanup as well. Any docs we upload will be self-hosted and we are going to use gh runners for everything not build bots.

[lamkina]

LGTM