minor #3220 [Site][minor] fix upson logo & url (smnandre)

This PR was merged into the 2.x branch.

Discussion
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[Site][minor] fix upson logo & url

| Q              | A
| -------------- | ---
| Bug fix?       | no
| New feature?   |  no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations?  |  no <!-- if yes, also update UPGRADE-*.md and src/**/CHANGELOG.md -->
| Documentation? | no <!-- required for new features, or documentation updates -->
| Issues         | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License        | MIT

Changed "platform.sh" name in footer into Upsun

Commits
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0feca0d [minor] fix upson logo & url

Author: Kocal

ux.symfony.com/templates/_footer.html.twig

@@ -38,10 +38,10 @@
                     <span class="d-block d-md-inline">
                         hosted with
                         <span style="font-weight: 700;">
-                            <a href="https://platform.sh"
-                               rel="external noopener noreferrer"
+                            <a href="https://upsun.com"
+                               rel="external"
                                style="font-weight: 700;"
-                            >Platform.sh</a>
+                            >Upsun</a>
                         </span>
                     </span>
                 </p>