Bump actions/checkout from v2 to v2.3.0 (#114)

Bumps [actions/checkout](https://github.com/actions/checkout) from v2 to v2.3.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/master/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...b4483adec309c0d01a5435c5e24eb40de5773ad9)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       -
         name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.0
       -
         name: Gen dummy page
         run: |

.github/workflows/labels.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       -
         name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.0
       -
         name: Run Labeler
         if: success()

.github/workflows/pre-checkin.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       -
         name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.0
       -
         name: Install
         run: yarn install