(fix) add download icon to thunderbird CTA

bedrock/products/templates/products/landing.html

@@ -38,6 +38,7 @@
 {% set _entrypoint = 'mozilla.org-products' %}
 
 {% set icon_external = '<span class="mzp-c-button-icon-end"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><g fill="none" fill-rule="evenodd" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"><path d="M13 4h7v7M12 12l8-8M8 4H7a3 3 0 0 0-3 3v10a3 3 0 0 0 3 3h10a3 3 0 0 0 3-3v-1"/></g></svg></span>' %}
+{% set icon_download ='<span class="mzp-c-button-icon-end"><svg xmlns="http://www.w3.org/2000/svg" xml:space="preserve" viewBox="0 0 16 16" width="16" height="16" fill="currentColor"><path d="M8 13c.2 0 .4-.1.5-.2l4.4-4.4-1.1-1.1-3.1 3.1V1H7.2v9.4L4.1 7.3l-1 1.1 4.4 4.4c.1.1.3.2.5.2z" /><path d="M13.5 12v2c0 .3-.2.5-.5.5H3c-.3 0-.5-.2-.5-.5v-2H1v2c0 1.1.9 2 2 2h10c1.1 0 2-.9 2-2v-2h-1.5z" /></svg></span>' %}
 
 {% block content %}
 <main>
@@ -179,7 +180,7 @@ <h3 class="mzp-c-picto-heading"><a href="https://developer.mozilla.org/{{ referr
     ) %}
       <h3 class="mzp-c-picto-heading"><a href="https://www.thunderbird.net/{{ referrals }}" data-cta-type="link" data-cta-text="Thunderbird" data-cta-position="heading">{{ ftl('firefox-products-thunderbird') }}</a></h3>
       <p>{{ ftl('firefox-products-access-all') }}</p>
-      <p><a class="mzp-c-button mzp-t-product" href="https://www.thunderbird.net/download/{{ referrals }}" rel="external noopener" data-cta-type="link" data-cta-text="Thunderbird Download">{{ ftl('firefox-products-download-thunderbird') }} {{ icon_external|safe }}</a></p>
+      <p><a class="mzp-c-button mzp-t-product" href="https://www.thunderbird.net/download/{{ referrals }}" rel="external noopener" data-cta-type="link" data-cta-text="Thunderbird Download">{{ ftl('firefox-products-download-thunderbird') }} {{ icon_download|safe }}</a></p>
     {% endcall %}
 
     <!-- Fakespot -->