Refactor utc tests (typos, test descriptions, code formatting) - splits pr #2084

[BePo65]

Fix typos in tests, duplicate test descriptions and improve code formatting.

This PR extracts parts of pr https://github.com/iamkun/dayjs/pull/2084 to make that PR more reviewable.

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (a947a51) 99.77% compared to head (5e9adc3) 99.77%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #2461   +/-   ##
=======================================
  Coverage   99.77%   99.77%           
=======================================
  Files         183      183           
  Lines        2262     2262           
  Branches      641      641           
=======================================
  Hits         2257     2257           
  Misses          5        5           

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