Remove checkout from auto-{approve, merge} actions (#298)

.github/workflows/approve.yml

@@ -9,7 +9,6 @@ jobs:
     if: "! startsWith(github.event.head_commit.message, '[CI Skip]') && (!github.event.pull_request || github.event.pull_request.head.repo.full_name == github.repository)"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
       - uses: jacogr/action-approve@master
         with:
           authors: jacogr

.github/workflows/merge.yml

@@ -8,7 +8,6 @@ jobs:
   auto-merge:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
       - uses: jacogr/action-merge@master
         with:
           checks: build,lint,test