Fix broken tests and stop testing nightly

[timholy]

Rationale for not testing nightly: https://discourse.julialang.org/t/why-do-packages-run-continuous-integration-tests-on-julia-nightly/101208/3?u=tim.holy

Explanation of the test failure: https://github.com/JuliaLang/julia/issues/50620

[codecov[bot]]

Codecov Report

Merging #224 (ca8b162) into master (7637195) will increase coverage by 0.14%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #224      +/-   ##
==========================================
+ Coverage   89.73%   89.87%   +0.14%     
==========================================
  Files           8        8              
  Lines         711      711              
==========================================
+ Hits          638      639       +1     
+ Misses         73       72       -1     

see 1 file with indirect coverage changes

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