Add transition to .progress-bar

- Pulls in values from v3
- Closes #22371 which didn't use a transition include

scss/_progress.scss

@@ -18,6 +18,7 @@
   line-height: $progress-height;
   color: $progress-bar-color;
   background-color: $progress-bar-bg;
+  @include transition($progress-bar-transition);
 }
 
 .progress-bar-striped {

scss/_variables.scss

@@ -828,6 +828,7 @@ $progress-box-shadow:           inset 0 .1rem .1rem rgba($black,.1) !default;
 $progress-bar-color:            $white !default;
 $progress-bar-bg:               $brand-primary !default;
 $progress-bar-animation-timing: 1s linear infinite !default;
+$progress-bar-transition:       width .6s ease !default;
 
 // List group