ci: upgrade to actions/checkout@v4

Author: cuviper

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         rust: [1.56.0, stable, beta, nightly]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v4
         if: startsWith(matrix.rust, '1')
         with:
@@ -27,7 +27,7 @@ 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
@@ -39,7 +39,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/[email protected]
         with:
           components: rustfmt

.github/workflows/master.yaml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         rust: [1.56.0, stable]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v4
         if: startsWith(matrix.rust, '1')
         with:

.github/workflows/pr.yaml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         rust: [1.56.0, stable]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v4
         if: startsWith(matrix.rust, '1')
         with:
@@ -27,7 +27,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/[email protected]
         with:
           components: rustfmt