build: Update test workflow to rely on oldstable/stable

x-ref: go-git/go-git#1769

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

Author: pjbgf

.github/workflows/test.yml

@@ -5,7 +5,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.21.x,1.22.x,1.23.x]
+        go-version: [1.24.x, oldstable, stable]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps: