hide-media-buttons.php

/**
 * Hide media buttons from the default editor.
 *
 * @param array  $settings  _WP_Editors::editor() settings.
 * @param string $editor_id Editor ID.
 * @return array (maybe) modified editor settings.
 */
function hide_media_buttons( $settings, $editor_id ) {
	if ( 'post' == get_post_type() && 'content' == $editor_id ) {
		$settings['media_buttons'] = false;
	}
	return $settings;
}
add_filter( 'wp_editor_settings', 'hide_media_buttons', 10, 2 );