More descriptive error on DynamicClient not initialized

[alexandrehassan]

Closes #416

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.33%. Comparing base (33c014b) to head (7f7d81e).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
kubernetes_asyncio/dynamic/client.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #422      +/-   ##
==========================================
- Coverage   28.33%   28.33%   -0.01%     
==========================================
  Files         915      915              
  Lines      108603   108606       +3     
==========================================
  Hits        30770    30770              
- Misses      77833    77836       +3     

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[tomplus]

Thank you for your contribution!