ci: reduce Go matrix to representative versions

[xgopilot]

Requested by @luoliwoshang

Summary

• Reduced Go version matrix from ["1.21.13", "1.22.12", "1.23.6", "1.24.2"] to ["1.21.13", "1.24.2"]
• Updated both llgo and hello jobs in .github/workflows/llgo.yml

Rationale

Most Go-related issues fall into two categories separated by Go 1.22 (alias support boundary):

• Pre–Go 1.22 (1.21.13) — no alias support
• Go 1.22+ (1.24.2) — alias supported, latest stable

This change:

• Reduces CI jobs from 8 to 4 for both llgo and hello jobs (50% reduction)
• Preserves coverage of the key semantic boundary at Go 1.22
• Enables better scalability as simulator tests are added

Fixes #1600

[luoliwoshang]

Hello job Current maybe not loss lots time,maybe keep the matrix here

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.06%. Comparing base (38d9fa2) to head (20183b6).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1601   +/-   ##
=======================================
  Coverage   91.06%   91.06%           
=======================================
  Files          45       45           
  Lines       11981    11981           
=======================================
  Hits        10911    10911           
  Misses        894      894           
  Partials      176      176           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.