Simplifying detection efficiency validation notebook.

[astronomerritt]

The notebook demonstrating the fading function/detection efficiency had a lot of extraneous code and while-loops instead of array operations, and was also missing an explanation of the fading function. I had to edit it anyway to make plots for the paper, so figured I may as well overhaul it while I was there.

Review Checklist for Source Code Changes

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.14%. Comparing base (c2b800c) to head (59c9f77).
Report is 249 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1035      +/-   ##
==========================================
+ Coverage   80.90%   81.14%   +0.23%     
==========================================
  Files          70       70              
  Lines        3148     3166      +18     
==========================================
+ Hits         2547     2569      +22     
+ Misses        601      597       -4     

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