Remove dead code

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

import java.util.Collection;

import java.util.regex.Pattern;

import it.niedermann.owncloud.notes.R;

import it.niedermann.owncloud.notes.model.DBNote;

/**

 * Provides basic functionality for Note operations.

    public static String extendCategory(@NonNull String category) {

        return category.replace("/", " / ");

    }

    public static String concat(@NonNull Collection<DBNote> notes) {

        return "";

    }

}