Fix x86_64-apple-darwin build: replace retired macos-13 runner with macos-latest

macos-13 (x86) runners have been retired by GitHub. The x86_64-apple-darwin
target can be cross-compiled on macos-latest (arm64) using Rust's built-in
cross-compilation support — no behaviour change, just a supported runner.

https://claude.ai/code/session_01GzGtjMcwBXyVW3uKW4F2Ai

Author: claude

.github/workflows/release-build.yml

@@ -71,7 +71,7 @@ jobs:
             use-cross: false
 
           - target: x86_64-apple-darwin
-            os: macos-13
+            os: macos-latest
             artifact-name: stackql-deploy-macos-x86_64
             archive: tar.gz
             use-cross: false