I have checked your code , you have taken wrong referenceBlock.
Please use below code in your xml file (sales_email_order_shipment_track.xml)
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance dc" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<referenceBlock name="sales.order.email.shipment.track">
<action method="setTemplate">
<argument name="template" xsi:type="string">PackageName_Module::email/shipment/track.phtml</argument>
</action>
</referenceBlock>
</page>
Please create file track.phtml under path
PackageName/Module/view/frontend/templates/email/shipment/
Put below code :-
<?php
/**
* Copyright © Magento, Inc. All rights reserved.
* See COPYING.txt for license details.
*/
?>
<?php /* @var \Magento\Framework\View\Element\Template $block */ ?>
<?php $_shipment = $block->getShipment() ?>
<?php
/* @var \Magento\Sales\Model\Order $_order */
$_order = $block->getOrder() ?>
<?php if ($_shipment && $_order) : ?>
<?php $trackCollection = $_order->getTracksCollection($_shipment->getId()) ?>
<?php if ($trackCollection) : ?>
<br />
<table class="shipment-track">
<thead>
<tr>
<th><?= $block->escapeHtml(__('Shipped By dhwani')) ?></th>
<th><?= $block->escapeHtml(__('Tracking Number')) ?></th>
</tr>
</thead>
<tbody>
<?php foreach ($trackCollection as $_item) : ?>
<tr>
<td><?= $block->escapeHtml($_item->getTitle()) ?>:</td>
<td>
<a href="<?= $block->escapeUrl($block->getTrackingUrl()->getUrl($_item)) ?>" target="_blank">
<?= $block->escapeHtml($_item->getNumber()) ?>
</a>
</td>
</tr>
<?php endforeach ?>
</tbody>
</table>
<?php endif; ?>
<?php endif; ?>
In above code i have changed title like below to check it is working or not.
<th><?= $block->escapeHtml(__('Shipped By dhwani')) ?>
And i have got below output in email:-
https://prnt.sc/103grlp
