This button is removed in latest version 10.0 of odoo.

but if you want remove that button just comment this code or override it in addons/web/static/src/xml/base.xml from line 1023

<td>

    <a class="oe_form_binary_file_save_data">

        <button class="oe_button oe_form_binary_file_save" type="button" title="Save As">

            <img t-att-src='_s + "/web/static/src/img/icons/gtk-save.png"'/>

            <span>Save As</span>

        </button>

    </a>

</td>

and also comment the javascript or override it that depends on oe_form_binary_file_save class that used in above button in addons/web/static/src/js/views/form_widget.js

<field widget="binary" name="datas" filename="datas_fname"/>

                  <field name="datas_fname" readonly = "1" invisible="1"/>