chore(ci): test with 2.2.4 (nimbus) and 2.2.10

[gmelodie]

Summary

Drop support for Nim 2.0.16 and 2.2.6 in CI, replacing them with 2.2.10 and 2.2.4 respectively. This keeps the test matrix on actively maintained 2.2.x releases and removes the legacy 2.0.x line.

• .github/workflows/ci.yml:
  • Replaced v2.0.16 with v2.2.10 in the Nim version matrix
  • Replaced v2.2.6 with v2.2.4 in the Nim version matrix
• README.md:
  • Updated the supported Nim versions line from v2.0.16 and v2.2.6 to v2.2.4 and v2.2.10
  • Added missing newline at end of file

Affected Areas

• Gossipsub
• Transports
• Peer Management / Discovery
• Protocol Logic
• Build / Tooling

Two Nim versions in the CI matrix updated; no source changes.

• Other

Compatibility & Downstream Validation

No library code changed. All existing encode/decode and API paths are unaffected. Downstream consumers (Nimbus, Waku, Codex) should validate that their own builds are compatible with Nim 2.2.4 and 2.2.10 if they pin to the versions advertised here.

Impact on Library Users

• None — purely a CI and documentation change. No types, procs, or ABIs were modified.

Risk Assessment

• Nim 2.0.x dropped: Code that relied on 2.0.x-specific behaviour will no longer be caught by CI. Risk is low because 2.0.x is end-of-life and the codebase already targets 2.2.x.
• 2.2.6 → 2.2.4: Minor regression in tested patch version (older patch). Risk is low; 2.2.4 is a stable release and any regressions introduced between 2.2.4 and 2.2.6 would need to be re-verified manually.

References

#2339

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.39%. Comparing base (adb2743) to head (ef3ca90).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2343      +/-   ##
==========================================
- Coverage   73.42%   73.39%   -0.04%     
==========================================
  Files         168      168              
  Lines       22221    22221              
  Branches       20       20              
==========================================
- Hits        16316    16309       -7     
- Misses       5905     5912       +7     

see 2 files with indirect coverage changes

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[narimiran]

This only changes the tested Nim versions in ci.yml. Meaning that the CI job will test v2.2.4 and v2.2.10, but the daily jobs and interop tests will test v2.0.16 and v2.2.6. Is this mismatch intended?

[narimiran]

Or, more generally: I don't understand the point of this PR — why open this PR instead of commenting/modifying #2339 if something there needs changing?
On the first glance, that one looks more complete/correct. If it only needs changing v2.0.16 to v2.2.4, I can do that too. (But why did it then receive two approvals, including yours?)

[gmelodie]

@narimiran sure, please do