Docs: remove or replaced deprecated .text-bg-dark with .fg-white

Spotted in #42487

Author: julien-deramond

js/tests/visual/dialog.html

@@ -169,7 +169,7 @@ <h1 class="dialog-title">Non-Modal Dialog</h1>
 
       <br><br>
 
-      <div class="text-bg-dark p-2" id="tall" style="display: none;">
+      <div class="p-2" id="tall" style="display: none;">
         Tall body content to force the page to have a scrollbar.
       </div>
     </div>

site/src/assets/examples/features/index.astro

@@ -148,7 +148,7 @@ export const extra_css = ['features.css']
 
     <div class="row row-cols-1 lg:row-cols-3 align-items-stretch g-4 py-5">
       <div class="col">
-        <div class="card card-cover h-100 overflow-hidden text-bg-dark rounded-4 shadow-lg" style="background-image: url('unsplash-photo-1.jpg');">
+        <div class="card card-cover h-100 overflow-hidden rounded-4 shadow-lg" style="background-image: url('unsplash-photo-1.jpg');">
           <div class="d-flex flex-column h-100 p-5 pb-3 fg-white text-shadow-1">
             <h3 class="pt-5 mt-5 mb-4 display-6 lh-1 fw-bold">Short title, long jacket</h3>
             <ul class="d-flex list-unstyled mt-auto">
@@ -169,7 +169,7 @@ export const extra_css = ['features.css']
       </div>
 
       <div class="col">
-        <div class="card card-cover h-100 overflow-hidden text-bg-dark rounded-4 shadow-lg" style="background-image: url('unsplash-photo-2.jpg');">
+        <div class="card card-cover h-100 overflow-hidden rounded-4 shadow-lg" style="background-image: url('unsplash-photo-2.jpg');">
           <div class="d-flex flex-column h-100 p-5 pb-3 fg-white text-shadow-1">
             <h3 class="pt-5 mt-5 mb-4 display-6 lh-1 fw-bold">Much longer title that wraps to multiple lines</h3>
             <ul class="d-flex list-unstyled mt-auto">
@@ -190,8 +190,8 @@ export const extra_css = ['features.css']
       </div>
 
       <div class="col">
-        <div class="card card-cover h-100 overflow-hidden text-bg-dark rounded-4 shadow-lg" style="background-image: url('unsplash-photo-3.jpg');">
-          <div class="d-flex flex-column h-100 p-5 pb-3 text-shadow-1">
+        <div class="card card-cover h-100 overflow-hidden rounded-4 shadow-lg" style="background-image: url('unsplash-photo-3.jpg');">
+          <div class="d-flex flex-column h-100 p-5 pb-3 fg-white text-shadow-1">
             <h3 class="pt-5 mt-5 mb-4 display-6 lh-1 fw-bold">Another longer title belongs here</h3>
             <ul class="d-flex list-unstyled mt-auto">
               <li class="me-auto">