Bump actions/checkout from 3 to 4 (#9)

Author: dependabot[bot]

.github/workflows/rust.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/cache@v3
       with:
         path: |
@@ -41,7 +41,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/cache@v3
       with:
         path: |