Hello @nazmussakib56,
If you need to hide only the vendor registration, You are unable to make the change by default. You can hide the vendor registration button.
/wp-content/plugins/dokan-lite/templates/global/seller-registration-form.php
Comment out line no: 68-71
<label>
<input type="radio" name="role" value="seller"<?php checked( $role, 'seller' ); ?>> <?php esc_html_e( 'I am a vendor', 'dokan-lite' ); ?>
</label>
Use // to comment out. Make the changes using a child theme so that you do not lose the changes during an update. It is recommended to use a child theme during such modification. The mentioned link can be useful to you for the purpose: https://wpdoctor.press/overriding-dokan-plugin-template-easy/
I hope this helps. Please check and let me know the result.
Best Regards ??