Bump actions/checkout from 3 to 4 (#84)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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>

.github/workflows/concat-kdf.yml

@@ -28,7 +28,7 @@ jobs:
           - thumbv7em-none-eabi
           - wasm32-unknown-unknown
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
@@ -43,7 +43,7 @@ jobs:
           - 1.56.0 # MSRV
           - stable
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}

.github/workflows/hkdf.yml

@@ -28,7 +28,7 @@ jobs:
           - thumbv7em-none-eabi
           - wasm32-unknown-unknown
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: RustCrypto/actions/cargo-cache@master
       - uses: dtolnay/rust-toolchain@master
         with:
@@ -49,7 +49,7 @@ jobs:
           - 1.41.0 # MSRV
           - stable
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: RustCrypto/actions/cargo-cache@master
       - uses: dtolnay/rust-toolchain@master
         with:

.github/workflows/workspace.yml

@@ -13,7 +13,7 @@ jobs:
   clippy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: RustCrypto/actions/cargo-cache@master
       - uses: dtolnay/rust-toolchain@master
         with:
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@master