build(deps): bump actions/checkout from 2.4.0 to 3.0.2 (#70)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.4.0 to 3.0.2.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2.4.0...v3.0.2)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

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

Author: dependabot[bot]

.github/workflows/book.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
       - name: Checkout
-        uses: actions/checkout@v2.4.0
+        uses: actions/checkout@v3.0.2
         with:
           persist-credentials: false
 

.github/workflows/main.yml

@@ -25,7 +25,7 @@ jobs:
         override: true
         components: rustfmt, clippy
 
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v3.0.2
 
     - name: Format
       uses: actions-rs/[email protected]
@@ -96,7 +96,7 @@ jobs:
         launchctl unload -w ${SL}/LaunchAgents/${PL}.plist
         sudo launchctl unload -w ${SL}/LaunchDaemons/${PL}.Root.plist
 
-    - uses: actions/checkout@v2.4.0
+    - uses: actions/checkout@v3.0.2
 
     - uses: actions-rs/[email protected]
       id: toolchain