miniDifi: bugfix for discovery options past discovery window

[mjuric]

Say our discovery window is 10, and the object has tracklets at nights:

2 4 6 8

This should generate the following discovery opportunities:

2 4 6
2 4 6 8
  4 6 8

The code before this bugfix would stop looking for discovery opportunities after the final night was reached, so it didn't "see" the last one combination.

Fixes # .

Describe your changes.

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

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 80.78%. Comparing base (a1548a3) to head (c661f54). Report is 70 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sorcha/modules/PPMiniDifi.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1002 +/- ## ========================================== - Coverage 80.89% 80.78% -0.12% ========================================== Files 69 69 Lines 3094 3107 +13 ========================================== + Hits 2503 2510 +7 - Misses 591 597 +6 ```

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[mjuric]

This codecov fail is bogus. You can verify by dropping the + window on that line, and seeing the unit tests fail. Blah.