ci: remove circleci dummy

[thaJeztah]

• follow-up ci: dummy circleci config #3119
• follow-up vendor: github.com/docker/docker v23.0.0 #3117 (comment)

I disabled/deleted the webhook, so we can remove this dummy.

- What I did

- How I did it

- How to test it

- Description for the changelog

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 14.74%. Comparing base (6e9e7b8) to head (258a1f0).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3253      +/-   ##
==========================================
+ Coverage   14.73%   14.74%   +0.01%     
==========================================
  Files         200      200              
  Lines       93077    93085       +8     
==========================================
+ Hits        13712    13730      +18     
+ Misses      78019    78010       -9     
+ Partials     1346     1345       -1     

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[thaJeztah]

LGTM