CI: correct date command for macOS runner

Signed-off-by: Stephen Gutekanst <stephen@sourcegraph.com>

Author: Stephen Gutekanst

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Release
         if: success() && github.ref == 'refs/heads/main' && github.event_Name == 'push' && github.repository == 'sourcegraph/doctree'
         run: |
-          export RELEASE_NAME="$(date --rfc-3339=date)-$RELEASE_COMMIT"
+          export RELEASE_NAME="$(date +%Y-%m-%d)-$RELEASE_COMMIT"
           gh release create "release-$RELEASE_NAME" --title "Release of main @ $RELEASE_COMMIT"
           gh release upload "release-$RELEASE_NAME" out/doctree-aarch64-macos
           gh release upload "release-$RELEASE_NAME" out/doctree-x86_64-linux