Changing default footprint_edge_threshold value

[astronomerritt]

Fixes #1038.

• Changed the default footprint_edge_threshold value in all configuration files packaged within Sorcha to 2.0arcsec, which is equivalent to the 10px value we got from DM.
• Minor edits to the text of the config files.
• Adjusted unit test.
• Regenerated goldens.

Review Checklist for Source Code Changes

• [x] Does pip install still work?
• [x] Have you written a unit test for any new functions?
• [x] Do all the units tests run successfully?
• [x] Does Sorcha run successfully on a test set of input files/databases?
• [x] Have you used black on the files you have updated to confirm python programming style guide enforcement?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.11%. Comparing base (bbece40) to head (f14c63f). Report is 7 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1039 +/- ## ========================================== - Coverage 81.14% 81.11% -0.04% ========================================== Files 70 70 Lines 3166 3166 ========================================== - Hits 2569 2568 -1 - Misses 597 598 +1 ```

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[astronomerritt]

Reverted the goldens :)