fix: replace deprecated $tc translation calls with $t

[Jozsef Damokos (jozsefdamokos)]

• Replace $tc() and Shopware.Snippet.tc() with $t() / Shopware.Snippet.t() across the admin module, core deprecates them for removal in 6.9 and reports every call since fix(administration): postpone the $tc removal to 6.9 and report deprecated i18n usages shopware#20775
• Pure rename, all multi-argument calls were already in the (key, named, count) order $t expects, and in 6.7.0.0 both names point at the same i18n.global.t
• Drop the tc declaration from the plugin's Shopware.Snippet typing and update the store spec mock

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.35%. Comparing base (5f3eee8) to head (08c1916).

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk     #237   +/-   ##
=========================================
  Coverage     65.35%   65.35%           
  Complexity     4786     4786           
=========================================
  Files           654      654           
  Lines         21753    21753           
=========================================
  Hits          14217    14217           
  Misses         7536     7536           

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