Bump GitHub Actions to v5 (Node.js 24) in release workflow

Summary:
Upgrades `actions/checkout`, `actions/upload-artifact`, and
`actions/download-artifact` from v4 to v5 in the release workflow.

GitHub is deprecating Node.js 20 on their runners on the following timeline:
  - 2026-06-02: Node.js 24 becomes the default; v4 actions are force-upgraded.
  - 2026-09-16: Node.js 20 is fully removed from runners; v4 breaks hard
                unless the action supports Node.js 24 natively.

The v5 majors of these three actions run on Node.js 24 natively, so bumping
now gets us ahead of the June 2 flip and avoids any surprise behaviour
changes mid-release.

Compatibility notes:
- `actions/checkout@v5` with `submodules: recursive` is drop-in compatible
  with v4 for our usage.
- `actions/upload-artifact@v5` keeps the v4 API (name + path) we rely on.
- `actions/download-artifact@v5` keeps `pattern: cibw-*` + `merge-multiple:
  true` behaviour unchanged. This exact pattern is in use across fbsource
  (e.g., `third-party/pypi/pyvinecopulib/*/pypi.yml`) on v5 already.

Reviewed By: aperez

Differential Revision: D103490665

fbshipit-source-id: 6c0137a5aca0390e33d99a8ae979f6a11452eb8a

Author: pdepetro

.github/workflows/release.yml

@@ -49,7 +49,7 @@ jobs:
         os: [ubuntu-latest, macos-latest]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
         with:
           submodules: recursive
 
@@ -91,7 +91,7 @@ jobs:
           CIBW_ENVIRONMENT_MACOS: MACOSX_DEPLOYMENT_TARGET=11.0
 
       - name: Upload wheels artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: cibw-wheels-${{ matrix.os }}
           path: ./wheelhouse/*.whl
@@ -102,15 +102,15 @@ jobs:
     timeout-minutes: 15
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
         with:
           submodules: recursive
 
       - name: Build sdist
         run: pipx run build --sdist
 
       - name: Upload sdist artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: cibw-sdist
           path: dist/*.tar.gz
@@ -127,7 +127,7 @@ jobs:
 
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v5
         with:
           pattern: cibw-*
           path: dist
@@ -151,7 +151,7 @@ jobs:
 
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v5
         with:
           pattern: cibw-*
           path: dist