test: fix lint warning and simplify locales test

[ST-DDT]

Fixes this lint warning:

[codecov]

Codecov Report

Merging #1430 (7a3136c) into main (f124bfb) will increase coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 7a3136c differs from pull request most recent head 9b7fb04. Consider uploading reports for the commit 9b7fb04 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1430   +/-   ##
=======================================
  Coverage   99.62%   99.62%           
=======================================
  Files        2166     2166           
  Lines      237450   237450           
  Branches     1041     1045    +4     
=======================================
+ Hits       236550   236568   +18     
+ Misses        879      861   -18     
  Partials       21       21           

Impacted Files	Coverage Δ
src/modules/internet/user-agent.ts	88.35% <0.00%> (+4.76%)	⬆️

[Shinigami92]

let's wait with that one until we merged

• test: extend vitest with (not) toContainDuplicates #1428
  that way we don't need to rewrite this PR twice

[xDivisionByZerox]

@ST-DDT Now I see what you wanted to do here. I'm sorry I did not understood at that time...

[ST-DDT]

No problem. I sometimes have trouble explaining my ideas/intentions.
If it wasn't for the lint error I wouldn't have proposed it again. Sadly, I didn't notice the lint warning last time.
In v8, I will likely set most warnings to error so that the pipeline fails and I don't have to pay attention anymore.