Resolve some bugs with the jump fitting algorithm

[WilliamJamieson]

This PR makes some adjustments to the jump detection algorithm so that it exactly detects the jumps detected in the simulated data.

Checklist

• [ ] added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• [ ] updated relevant tests
• [ ] updated relevant documentation
• [ ] updated relevant milestone(s)
• [ ] added relevant label(s)

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
tests/test_jump_cas22.py	98.34% <85.18%> (-1.66%)	:arrow_down:

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