ci: Update to actions/checkout@v4.

Author: waywardmonkeys

.github/workflows/ci.yaml

@@ -25,7 +25,7 @@ jobs:
           nightly,
         ]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
@@ -43,7 +43,7 @@ jobs:
       - run: |
           sudo apt-get update
           sudo apt-get install gcc-multilib
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with:
           target: i586-unknown-linux-gnu
@@ -54,7 +54,7 @@ jobs:
     name: No Std
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with:
           target: thumbv6m-none-eabi
@@ -65,7 +65,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@1.62.0
         with:
           components: rustfmt

.github/workflows/master.yaml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         rust: [1.31.0, stable]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}

.github/workflows/pr.yaml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         rust: [1.31.0, stable]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
@@ -25,5 +25,5 @@ jobs:
       - uses: dtolnay/rust-toolchain@1.62.0
         with:
           components: rustfmt
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: cargo fmt --all --check