ci: Replace deprecated macos-13 runner with macos-14

macos-13 runners are no longer available. Use macos-14 (ARM) and
cross-compile for x86_64 since the target is already explicit.

Author: lutter

.github/workflows/gnd-binary-build.yml

@@ -23,7 +23,7 @@ jobs:
             runner: ubuntu-22.04
             asset_name: gnd-linux-aarch64
           - target: x86_64-apple-darwin
-            runner: macos-13
+            runner: macos-14
             asset_name: gnd-macos-x86_64
           - target: aarch64-apple-darwin
             runner: macos-latest