ci: use another mirror for etcd image

[waynexia]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

Try to pull etcd from https://github.com/zcube/bitnami-compat/pkgs/container/bitnami-compat%2Fetcd to avoid rate limit. Another registry we can try is https://quay.io/repository/coreos/etcd?tab=tags&tag=latest

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.07%. Comparing base (aa125a5) to head (90da6d9).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3486      +/-   ##
==========================================
- Coverage   85.40%   85.07%   -0.34%     
==========================================
  Files         897      897              
  Lines      148106   148226     +120     
==========================================
- Hits       126495   126097     -398     
- Misses      21611    22129     +518     

[killme2008]

LGTM