Remove taxonomy widget from “PAGE” post

In your register_taxonomy() args, set meta_box_cb => false

‘meta_box_cb’
(bool|callable) Provide a callback function for the meta box display. If not set, post_categories_meta_box() is used for hierarchical taxonomies, and post_tags_meta_box() is used for non-hierarchical. If false, no meta box is shown.

$args = array(
               //other args 
               'meta_box_cb' => false,
                );

register_taxonomy( $args );