Update actions/checkout action to v6.0.3

Author: renovate[bot]

.github/workflows/ci.yml

@@ -55,7 +55,7 @@ jobs:
           apk add --no-cache git build-base pkgconf llvm llvm-dev llvm-static libxml2-dev bash curl
 
       - name: Checkout code
-        uses: actions/checkout@v6.0.2
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
 
       - name: Set up uv
         uses: astral-sh/setup-uv@v8.1.0
@@ -94,7 +94,7 @@ jobs:
     runs-on: ${{ matrix.target }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6.0.2
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
 
       - name: Install Nix
         uses: cachix/install-nix-action@v31
@@ -128,7 +128,7 @@ jobs:
         shell: msys2 {0}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6.0.2
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
 
       - uses: msys2/setup-msys2@v2.31.0
         with:
@@ -165,7 +165,7 @@ jobs:
     if: startsWith(github.ref, 'refs/tags/')
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6.0.2
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
 
       - name: Set up uv
         uses: astral-sh/setup-uv@v8.1.0