You will need to edit the tag.hbs file (Documents ▸ Publii ▸ sites ▸ YOUR_SITE ▸ input ▸ themes ▸ YOUR_THEME) as follow:
Change the following part of code:
<div class="hero wrapper">
<p>
{{ translate 'tags.description' }}
</p>
<h1>
{{ translate 'tags.tagsPageTitle' }}
<sup>({{tagsNumber}})</sup>
</h1>
</div>
to:
<div class="hero wrapper">
<h1>
{{ translate 'tags.tagsPageTitle' }}
<sup>({{tagsNumber}})</sup>
</h1>
<p>
{{ translate 'tags.description' }}
</p>
</div>
To preserve your custom code and prevent it being overwritten the next time the theme is updated, please ensure that you have created override files; these are, essentially, copies of the existing theme files that are stored separately from the main theme files → https://getpublii.com/dev/theme-overrides/