Auto merge of rust-lang#83201 - klensy:checkout-v2, r=pietroalbini

use checkout@v2 in CI for master

Updates CI workflow to use checkout@v2 from v1 (as other parts of CI) for master, plus slightly faster checkout as result
compare v2
https://github.com/rust-lang-ci/rust/commit/2ccf06302c08d7d4911aad40e66a9a3ee731c6f9/checks/2113902859/logs
and v1 logs
https://github.com/rust-lang-ci/rust/commit/2ccf06302c08d7d4911aad40e66a9a3ee731c6f9/checks/2115229351/logs

Author: bors

.github/workflows/ci.yml

@@ -622,7 +622,7 @@ jobs:
     if: "github.event_name == 'push' && github.ref == 'refs/heads/master' && github.repository == 'rust-lang-ci/rust'"
     steps:
       - name: checkout the source code
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 2
       - name: publish toolstate

src/ci/github-actions/ci.yml

@@ -655,7 +655,7 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/master' && github.repository == 'rust-lang-ci/rust'
     steps:
       - name: checkout the source code
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 2