Docs: remove unused class in the homepage (#40900)

Co-authored-by: Julien Déramond <juderamond@gmail.com>

site/layouts/partials/home/get-started.html

@@ -6,7 +6,7 @@ <h2 class="display-5 mb-3 fw-semibold lh-sm">Get started any way you&nbsp;want</
   <p class="lead fw-normal">
     Jump right into building with Bootstrap—use the CDN, install it via package manager, or download the source code.
   </p>
-  <p class="d-flex justify-content-md-start justify-content-md-center lead fw-normal">
+  <p class="d-flex justify-content-md-center lead fw-normal">
     <a href="/docs/{{ .Site.Params.docs_version }}/getting-started/download/" class="icon-link icon-link-hover fw-semibold ps-md-4">
       Read installation docs
       <svg class="bi" aria-hidden="true"><use xlink:href="#arrow-right"></use></svg>