Update actions/checkout action to v3 (#3234)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

.github/workflows/docs.yml

@@ -8,7 +8,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
           node-version: 12.x

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
           node-version: 12.x
@@ -36,7 +36,7 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 2
       - uses: actions/setup-node@v3
@@ -58,7 +58,7 @@ jobs:
   slither:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
           node-version: 12.x