[stable5.1] fix: always show alarm unit in pural

[backportbot]

Backport of PR #6752

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 14.54%. Comparing base (231b73d) to head (4b35ba6).
Report is 3 commits behind head on stable5.1.

Files with missing lines	Patch %	Lines
...rc/components/Editor/Alarm/AlarmTimeUnitSelect.vue	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           stable5.1    #6755   +/-   ##
==========================================
  Coverage      14.54%   14.54%           
==========================================
  Files            210      210           
  Lines           9818     9818           
  Branches        2308     2308           
==========================================
  Hits            1428     1428           
  Misses          8064     8064           
  Partials         326      326           

Flag	Coverage Δ
javascript	14.54% <0.00%> (ø)

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