Drop macOS x86_64 desktop build (macos-13 runners unavailable)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mikkeldamsgaard

.github/workflows/release.yml

@@ -75,9 +75,6 @@ jobs:
           - os: macos-latest
             target: aarch64-apple-darwin
             artifact: ralph-desktop-macos-arm64
-          - os: macos-13
-            target: x86_64-apple-darwin
-            artifact: ralph-desktop-macos-x86_64
           - os: windows-latest
             target: x86_64-pc-windows-msvc
             artifact: ralph-desktop-windows-x86_64