fix(NcButton): do not reduce border radius for small buttons

[susnux]

☑️ Resolves

• Fix Don't reduce border radius of small buttons #8117

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[susnux]

/backport to stable8

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.77%. Comparing base (54c7810) to head (8be1fc5).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8129   +/-   ##
=======================================
  Coverage   52.77%   52.77%           
=======================================
  Files         103      103           
  Lines        3348     3348           
  Branches      976      976           
=======================================
  Hits         1767     1767           
  Misses       1333     1333           
  Partials      248      248           

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