use stable/oldstable, 1.23 and 1.21

Author: ndyakov

.github/workflows/build.yml

@@ -82,7 +82,8 @@ jobs:
           go-version:
             - "1.21.x"
             - "1.23.x"
-            - "1.24.x"
+            - oldstable
+            - stable
 
     steps:
       - name: Checkout code