fix(social): use shareArticle endpoint for LinkedIn share

The share-offsite endpoint opens blank modals. Using shareArticle
with mini=true pre-populates the URL in the compose field.

Author: RickCogley

src/_includes/templates/post-share.vto

@@ -14,7 +14,7 @@
     <a
       class="group -m-1 p-1"
       aria-label="{{ i18n.social.linkedin_share }}"
-      href="https://www.linkedin.com/sharing/share-offsite/?url={{ url }}"
+      href="https://www.linkedin.com/shareArticle?mini=true&url={{ url }}"
       target="_blank"
       rel="noopener"
     ><img