Bump actions/cache from 3 to 4 (#56)

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yaml

@@ -41,7 +41,7 @@ jobs:
       - name: Put pip binary directory into path
         run: echo "~/.local/bin" >> $GITHUB_PATH
       - name: Cache Cargo installed binaries
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache-cargo
         with:
           path: ~/cargo-bin

.github/workflows/nightlies.yaml

@@ -27,7 +27,7 @@ jobs:
           components: rustfmt
           override: true
       - name: Cache Cargo installed binaries
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         id: cache-cargo
         with:
           path: ~/cargo-bin