Add FXIOS-10831 Ensure reader mode URLs don't get sent to other devic…

…es. (#23868)

Ensure reader mode URLs don't get sent to other devices.

firefox-ios/Client/Frontend/Share/CustomAppActivity.swift

@@ -63,7 +63,9 @@ class CustomAppActivity: UIActivity, AppActivityProtocol {
 
     init(activityType: CustomActivityAction, url: URL) {
         self.appActivityType = activityType
-        self.url = url
+        self.url = url.isReaderModeURL
+                   ? (url.decodeReaderModeURL ?? url)
+                   : url
         super.init()
     }
 }