Revert "last updated on" from #36924 (#40907)

Only adding the text "Last updated on" was a misinterpretation of
#35379.
We're currently calling the publish date the last updated date on the
website, but the publish date usually isn't updated when a change is
made to an article. Until we can automatically update this date field
based on when the file itself was last updated, we should revert to the
original behavior.

website/views/pages/articles/basic-article.ejs

@@ -34,7 +34,7 @@
         </div>
         <div class="d-flex flex-sm-row flex-column justify-content-between align-items-sm-center">
           <div purpose="article-details" class="d-flex align-items-sm-center">
-            <span>Last updated on <js-timestamp format="billing" :at="thisPage.meta.publishedOn"></js-timestamp></span>
+            <span><js-timestamp format="billing" :at="thisPage.meta.publishedOn"></js-timestamp></span>
             <span  purpose="divider" class="px-2">|</span>
             <% if(articleCategorySlug !== 'customers') { %>
               <div purpose="article-author" class="d-flex flex-row align-items-center">
@@ -114,7 +114,7 @@
           </div>
           <div class="d-flex flex-sm-row flex-column justify-content-between align-items-sm-center">
             <div purpose="article-details" class="d-flex flex-row align-items-center">
-              <span>Last updated on <js-timestamp format="billing" :at="thisPage.meta.publishedOn"></js-timestamp></span>
+              <span><js-timestamp format="billing" :at="thisPage.meta.publishedOn"></js-timestamp></span>
               <% if(articleCategorySlug !== 'customers') { %>
                 <span class="px-2">|</span>
                 <img style="height: 28px; width: 28px; border-radius: 100%;" alt="The author's GitHub profile picture" :src="'https://github.com/'+thisPage.meta.authorGitHubUsername+'.png?size=200'">