Restrict access to the locking UI and the Code Editor to Administrators.

functions.php

/**
 * Restrict access to the locking UI and the Code Editor
 * to Administrators.
 * 
 * @param array $settings Default editor settings.
 * @param WP_Block_Editor_Context $context The current block editor context.
 */
function example_theme_restrict_locking_ui( $settings, $context ) {
    $is_administrator = current_user_can( 'activate_plugins' );

    if ( ! $is_administrator ) {
        $settings[ 'canLockBlocks' ] = false;
        $settings[ 'codeEditingEnabled' ] = false;
    }

	return $settings;
}
add_filter( 'block_editor_settings_all', 'example_theme_restrict_locking_ui', 10, 2 );