@NonNull
    static Single<Boolean> removeFromWatchlist(@NonNull final Geocache cache) {
        return addToOrRemoveFromWatchlist(cache, false);
    }
Removes the cache from the watch list

@param cache the cache to remove
@return {@code false} if an error occurred, {@code true} otherwise
main/src/main/java/cgeo/geocaching/connector/gc/GCParser.java