workflows: use checkout action v2 (#1775)
workflows: use checkout action v2 (#1775)

* Update git workflow

* Update .github/workflows/main.yml

Co-authored-by: Erik Zhang <c195b508e6f0c57aeafdb5e96947e2b79e6a4b40@neo.org>

Co-authored-by: Erik Zhang <c195b508e6f0c57aeafdb5e96947e2b79e6a4b40@neo.org>
AntShares/AntShares