Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v3)

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

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

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     name: Check formatting
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions-rs/toolchain@v1
       with:
           toolchain: nightly
@@ -25,7 +25,7 @@ jobs:
     name: Check that examples build
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions-rs/toolchain@v1
       with:
           toolchain: stable
@@ -37,7 +37,7 @@ jobs:
     name: Check that the code builds
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions-rs/toolchain@v1
       with:
           toolchain: stable
@@ -49,7 +49,7 @@ jobs:
     name: Check that examples build
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions-rs/toolchain@v1
       with:
           toolchain: stable
@@ -85,7 +85,7 @@ jobs:
       with:
         crate: cargo-dinghy
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - uses: actions-rs/toolchain@v1
       with:
           toolchain: stable