Fix fish shell completions

[synfinatic]

Original code didn't work at all and failed to install if the ~/.config/fish/completions/ directory didn't exist

[synfinatic]

I think this is a better fix than #497.

[codecov]

Codecov Report

Merging #622 (55a9693) into main (e893b9f) will increase coverage by 0.02%.
Report is 7 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #622      +/-   ##
==========================================
+ Coverage   82.46%   82.48%   +0.02%     
==========================================
  Files          35       35              
  Lines        3244     3247       +3     
==========================================
+ Hits         2675     2678       +3     
  Misses        501      501              
  Partials       68       68              

Files	Coverage Δ
internal/utils/fileedit.go	73.33% <100.00%> (+0.68%)	⬆️

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