mac build: set minimum system version to 10.13.0 in Info.plist

based on 907e5e7009

This way users get more feedback from the OS when they attempt to launch the app on old macOS.

Co-authored-by: Calin Culianu <calin.culianu@gmail.com>

contrib/osx/osx.spec

@@ -129,5 +129,6 @@ app = BUNDLE(
                 'CFBundleURLName': 'bitcoin',
                 'CFBundleURLSchemes': ['bitcoin', 'lightning', ],
             }],
+        'LSMinimumSystemVersion': '10.13.0',
     },
 )