chore: fix switch typo

[ZaneL1u]

This pull request addresses several typographical errors in the packages/vant/src/calendar component files. The most important changes include correcting the spelling of "switch" in various files.

Typographical corrections:

• packages/vant/src/calendar/CalendarHeader.tsx: Fixed the class name typo from with-swicth to with-switch.
• packages/vant/src/calendar/demo/index.vue: Corrected the import statement and component usage from SwicthModeField to SwitchModeField. [1] [2]
• packages/vant/src/calendar/index.less: Fixed the CSS class name typo from with-swicth to with-switch.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.68%. Comparing base (10b72e8) to head (7278e04).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13201      +/-   ##
==========================================
+ Coverage   89.59%   89.68%   +0.08%     
==========================================
  Files         257      257              
  Lines        7006     7006              
  Branches     1733     1733              
==========================================
+ Hits         6277     6283       +6     
+ Misses        386      380       -6     
  Partials      343      343              

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[inottn]

Nice catch 👍

[chenjiahan]

Thanks!