Resolve deprecated-enum-float-conversion compiler warnings

- Observed on macOS Monterey 12.7.6 with cmake version 4.0.1, Homebrew clang version 20.1.4, Target: x86_64-apple-darwin21.6.0

src/lib/platform/OSXScreen.mm

@@ -54,10 +54,7 @@ enum
   kDeskflowMouseScrollAxisY = 'saxy'
 };
 
-enum
-{
-  kCarbonLoopWaitTimeout = 10
-};
+static const double kCarbonLoopWaitTimeout = 10.0;
 
 int getSecureInputEventPID();
 std::string getProcessName(int pid);