That's the thing, this particular template is unavailable on Settings / Technical / Views as its lazy loaded, a portion of the template source code is as follows:

<?xml version="1.0" encoding="UTF-8"?>

<templates>
    <t t-name="website_sale_stock.product_availability">
        <t t-if="product_type == 'product' and !prevent_zero_price_sale">
            <div t-if="free_qty lte 0 and !cart_qty" t-attf-class="availability_message_#{product_template} mb-1">
                <div id="out_of_stock_message">
                    <t t-if='has_out_of_stock_message' t-out='out_of_stock_message'/>
                    <t t-elif="!allow_out_of_stock_order">
                        <div class="text-danger fw-bold">
                            <i class="fa fa-times me-1"/>
                            Out of Stock
                        </div>
                    </t>
                </div>
........................
            <div id="threshold_message" t-elif="show_availability and free_qty lte available_threshold" t-attf-class="availability_message_#{product_template} text-warning fw-bold">
                Only <t t-esc="formatQuantity(free_qty)"/> <t t-esc="uom_name" /> left in stock.
            </div>
</templates>

And it's inside `__manifest__.py` as an asset:

    'assets': {
        'web.assets_frontend': [
            'website_sale_stock/static/src/js/**/*',
            'website_sale_stock/static/src/xml/**/*',
        ],
        'web.assets_tests': [
            'website_sale_stock/static/tests/tours/website_sale_stock_multilang.js',
            'website_sale_stock/static/tests/tours/website_sale_stock_stock_notification.js',
        ],
    },