Replace match with let ... else where applicable

[JSorngard]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 89.62%. Comparing base (68598a4) to head (fe95835).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/generate.rs	50.00%	1 Missing ⚠️
src/sieve.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #102      +/-   ##
==========================================
- Coverage   89.65%   89.62%   -0.04%     
==========================================
  Files          11       11              
  Lines         996      993       -3     
==========================================
- Hits          893      890       -3     
  Misses        103      103              

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[JSorngard]

If these lines are not covered, they weren't before either. If I haven't made any mistakes those lines are also unreachable.