Bump actions/checkout from 1 to 4 (#228)

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Lloyd <lloydmeta@users.noreply.github.com>

.github/workflows/benchmarks.yml

@@ -8,7 +8,7 @@ jobs:
   benchmark:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: rustup toolchain update nightly && rustup default nightly
       - uses: Swatinem/rust-cache@v2
       - name: run benchmark

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     name: Basic sanity checks
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
@@ -34,7 +34,7 @@ jobs:
         toolchain: [ stable, nightly ]
         use_std: [ y, n ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         name: thumbv6m-none-eabi toolchain setup
         if: ${{ matrix.use_std == 'y' }}
@@ -71,7 +71,7 @@ jobs:
         toolchain: [ stable, nightly ]
         use_std: [ y, n ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         name: thumbv6m-none-eabi toolchain setup
         if: ${{ matrix.use_std == 'y' }}
@@ -113,7 +113,7 @@ jobs:
       matrix:
         toolchain: [ stable, nightly ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
@@ -133,7 +133,7 @@ jobs:
       matrix:
         toolchain: [ stable, nightly ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal

.github/workflows/rustdoc.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
 
       - uses: actions-rs/toolchain@v1
         with: