ci: update version of Cache action (#239)

Bump version of `actions/cache` from `@v3` to `@v4`, as recommended by
warnings in CI runs
(https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/).

Author: matthieu-d4r

.github/workflows/python-checks.yml

@@ -26,7 +26,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
 
       - name: Cargo cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry/index/
@@ -74,7 +74,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
 
       - name: Cargo cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry/index/

.github/workflows/rust-checks.yml

@@ -47,7 +47,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
 
       - name: Cargo cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cargo/registry/index/