changelog: add note from CVE-2025-22869

[ivanvc]

Adds entries regarding the golang.org/x/crypto upgrade to 0.35.0, to address CVE-2025-22869.

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.93%. Comparing base (d83346b) to head (7a241dc).
Report is 1 commits behind head on main.

Additional details and impacted files

see 17 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #19479      +/-   ##
==========================================
- Coverage   69.07%   68.93%   -0.15%     
==========================================
  Files         420      420              
  Lines       35762    35762              
==========================================
- Hits        24704    24653      -51     
- Misses       9647     9687      +40     
- Partials     1411     1422      +11     

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