macOS: remove manual invalidateRestorableState() (#12464)

This should be safe to delete now after #12461.

I tested saving 27 tabs, 4 with 2 splits,
`TerminalRestorable.encode(with:` finished successfully.

And I check the breakpoints when the Sparkle sends
`-[NSRunningApplication treminate]`. The call stack at `-[NSResponder
invalidateRestorableState]` is pretty much the same as quitting via
`cmd+q`.

macos/Sources/Features/Update/UpdateDelegate.swift

@@ -31,12 +31,4 @@ extension UpdateDriver: SPUUpdaterDelegate {
         ))
         return true
     }
-
-    func updaterWillRelaunchApplication(_ updater: SPUUpdater) {
-        // When the updater is relaunching the application we want to get macOS
-        // to invalidate and re-encode all of our restorable state so that when
-        // we relaunch it uses it.
-        NSApp.invalidateRestorableState()
-        for window in NSApp.windows { window.invalidateRestorableState() }
-    }
 }