chore: remove update logs UI from preferences

Remove the Show/Hide Logs button and logs view from the Updates preferences
tab. Keep the logging infrastructure in SparkleUpdater for diagnostics,
but don't display it in the UI.

Sources/ViewModels/SparkleUpdater.swift

@@ -10,7 +10,6 @@ final class SparkleUpdater: NSObject, ObservableObject {
     private let logger = Logger(subsystem: "net.24unix.iKeyMon", category: "Sparkle")
     private let verboseLogging: Bool
     @Published var logMessages: [String] = []
-    @Published var showLogs: Bool = false
 
     override init() {
         self.verboseLogging = ProcessInfo.processInfo.environment["SPARKLE_VERBOSE_LOGGING"] == "1"