ci: reduce Go matrix to representative versions

Keep only Go 1.21.13 (pre-Go 1.22) and Go 1.24.2 (latest stable)
to cover the key semantic boundary at Go 1.22 alias support.

This reduces CI jobs while preserving meaningful coverage.

Fixes #1600

Generated with [codeagent](https://github.com/qbox/codeagent)
Co-authored-by: luoliwoshang <51194195+luoliwoshang@users.noreply.github.com>

Author: xgopilot

.github/workflows/llgo.yml

@@ -43,7 +43,7 @@ jobs:
           - macos-latest
           - ubuntu-latest
         llvm: [19]
-        go: ["1.21.13", "1.22.12", "1.23.6", "1.24.2"]
+        go: ["1.21.13", "1.24.2"]
     runs-on: ${{matrix.os}}
     steps:
       - uses: actions/checkout@v6
@@ -217,7 +217,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest]
         llvm: [19]
-        go: ["1.21.13", "1.22.12", "1.23.6", "1.24.2"]
+        go: ["1.21.13", "1.24.2"]
     runs-on: ${{matrix.os}}
     steps:
       - uses: actions/checkout@v6