Bump actions/checkout from 2 to 3 (#67)

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -30,7 +30,7 @@ jobs:
           - os: windows-latest
             version: '1.6'
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: julia-actions/setup-julia@v1
         with:
           version: ${{ matrix.version }}
@@ -48,7 +48,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: julia-actions/setup-julia@v1
         with:
           version: '1'
@@ -66,7 +66,7 @@ jobs:
     name: Doctests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: julia-actions/setup-julia@v1
         with:
           version: '1'