Disabled link cleanup (#34886)

* Disabled link cleanup

per https://www.w3.org/TR/html-aria/#docconformance

> It is NOT RECOMMENDED to use `aria-disabled="true"` on an `a` element with an `href` attribute.
>
>NOTE
>If a link needs to be "disabled", remove the `href` attribute.

This PR removes the unnecessary `href="#"`, `tabindex="-1"`, and `aria-disabled="true"` from disabled links in both docs pages and examples. `aria-disabled="true"` *is* kept for disabled link-based buttons (that have `role="button"`) as there it's appropriate to use (you *want* to convey to assistive technologies that this thing you're claiming is a button is also disabled at the moment)

Further, the PR extends the "Link functionality caveat" to show the "proper" way (removing `href` and adding `.disabled` class only) to disable a link, but then explains what to do if that's not possible (and then keeps an example with all the traditional `href="#" tabindex="-1" aria-disabled="true"`, but explains clearly that it's not ideal). Same sort of explanation is also added to the pointer event utilities page

* Turn big note into actual normal doc text

Co-authored-by: Mark Otto <markd.otto@gmail.com>

Co-authored-by: Mark Otto <markd.otto@gmail.com>
Co-authored-by: XhmikosR <xhmikosr@gmail.com>

site/content/docs/5.1/examples/cheatsheet-rtl/index.html

@@ -1157,7 +1157,7 @@ direction: rtl
           <a class="nav-link active" aria-current="page" href="#">نشط</a>
           <a class="nav-link" href="#">رابط</a>
           <a class="nav-link" href="#">رابط</a>
-          <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">معطل</a>
+          <a class="nav-link disabled">معطل</a>
         </nav>
         {{< /example >}}
 
@@ -1194,7 +1194,7 @@ direction: rtl
             <a class="nav-link" href="#">رابط</a>
           </li>
           <li class="nav-item">
-            <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">معطل</a>
+            <a class="nav-link disabled">معطل</a>
           </li>
         </ul>
         {{< /example >}}
@@ -1237,7 +1237,7 @@ direction: rtl
                   </ul>
                 </li>
                 <li class="nav-item">
-                  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">معطل</a>
+                  <a class="nav-link disabled">معطل</a>
                 </li>
               </ul>
               <form class="d-flex">
@@ -1276,7 +1276,7 @@ direction: rtl
                   </ul>
                 </li>
                 <li class="nav-item">
-                  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">معطل</a>
+                  <a class="nav-link disabled">معطل</a>
                 </li>
               </ul>
               <form class="d-flex">
@@ -1332,7 +1332,7 @@ direction: rtl
         <nav aria-label="مثال آخر لترقيم الصفحات">
           <ul class="pagination pagination-lg flex-wrap">
             <li class="page-item disabled">
-              <a class="page-link" href="#" tabindex="-1" aria-disabled="true">السابق</a>
+              <a class="page-link">السابق</a>
             </li>
             <li class="page-item"><a class="page-link" href="#">1</a></li>
             <li class="page-item active" aria-current="page">