prevent multiple bookmark creation
prevent multiple bookmark creation

Fix for #451 “Multiple bookmarks created when trying to remove
bookmark” this is actually something that can happen by quickly tapping
on the button, regardless of when. Adding the flag should prevent
multiple entries into this method.

brave/browser-ios,brave/browser-ios,brave/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios