chore(ci): upgrade actions/checkout to v6

Author: paolobarbolini

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     name: cargo-deny
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: EmbarkStudios/cargo-deny-action@v2
 
@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: dtolnay/[email protected]
         with:
@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: dtolnay/[email protected]
         with:
@@ -59,7 +59,7 @@ jobs:
             rust: 1.83.0
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: dtolnay/rust-toolchain@master
         with: