Update actions/checkout action to v3 (mainmatter#1480)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3.0.0
       - uses: pnpm/[email protected]
         with:
           version: ${{ env.PNPM_VERSION }}
@@ -51,7 +51,7 @@ jobs:
           - ember-lts-3.28
 
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3.0.0
       - uses: pnpm/[email protected]
         with:
           version: ${{ env.PNPM_VERSION }}

.github/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3.0.0
       - uses: pnpm/[email protected]
         with:
           version: ${{ env.PNPM_VERSION }}