Remove 'xs' from text utilities (#21217)

docs/examples/album/index.html

@@ -43,7 +43,7 @@
       </div>
     </div>
 
-    <section class="jumbotron text-xs-center">
+    <section class="jumbotron text-center">
       <div class="container">
         <h1 class="jumbotron-heading">Album example</h1>
         <p class="lead text-muted">Something short and leading about the collection below—its contents, the creator, etc. Make it short and sweet, but not too short so folks don't simply skip over it entirely.</p>

docs/examples/carousel/index.html

@@ -51,7 +51,7 @@
         <div class="carousel-item active">
           <img class="first-slide" src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" alt="First slide">
           <div class="container">
-            <div class="carousel-caption text-xs-left">
+            <div class="carousel-caption text-left">
               <h1>Example headline.</h1>
               <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies vehicula ut id elit.</p>
               <p><a class="btn btn-lg btn-primary" href="#" role="button">Sign up today</a></p>
@@ -71,7 +71,7 @@
         <div class="carousel-item">
           <img class="third-slide" src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" alt="Third slide">
           <div class="container">
-            <div class="carousel-caption text-xs-right">
+            <div class="carousel-caption text-right">
               <h1>One more for good measure.</h1>
               <p>Cras justo odio, dapibus ac facilisis in, egestas eget quam. Donec id elit non mi porta gravida at eget metus. Nullam id dolor id nibh ultricies vehicula ut id elit.</p>
               <p><a class="btn btn-lg btn-primary" href="#" role="button">Browse gallery</a></p>

docs/examples/dashboard/index.html

@@ -92,7 +92,7 @@
         <main class="col-sm-9 offset-sm-3 col-md-10 offset-md-2 pt-3">
           <h1>Dashboard</h1>
 
-          <section class="row text-xs-center placeholders">
+          <section class="row text-center placeholders">
             <div class="col-6 col-sm-3 placeholder">
               <img src="data:image/gif;base64,R0lGODlhAQABAIABAAJ12AAAACwAAAAAAQABAAACAkQBADs=" width="200" height="200" class="img-fluid rounded-circle" alt="Generic placeholder thumbnail">
               <h4>Label</h4>