style: document the requirement to remove the ion-hide class

Author: brandyscarney

core/src/components/back-button/test/basic/index.html

@@ -125,7 +125,7 @@ <h3>Custom</h3>
 
         <ion-toolbar color="dark">
           <ion-buttons slot="start">
-            <ion-back-button class="ion-hide"></ion-back-button>
+            <ion-back-button class="ion-display-none"></ion-back-button>
           </ion-buttons>
           <ion-title>Hidden</ion-title>
         </ion-toolbar>

core/src/components/progress-bar/progress-bar.tsx

@@ -107,6 +107,7 @@ const renderProgress = (value: number, buffer: number) => {
      * When finalBuffer === 1, we use display: none
      * instead of removing the element to avoid flickering.
      */
+    // TODO(FW-6697): change `ion-hide` class to `ion-display-none` or another class
     <div
       class={{ 'buffer-circles-container': true, 'ion-hide': finalBuffer === 1 }}
       style={{ transform: `translateX(${finalBuffer * 100}%)` }}