fix(tab): rollback a11y implementation

Author: joselrio

core/src/components/tab/tab.tsx

@@ -55,12 +55,7 @@ export class Tab implements ComponentInterface {
 
   @Watch('active')
   changeActive(isActive: boolean) {
-    if (isActive) {
-      // ensure tabindex gets updated before setting focus to the element
-      setTimeout(() => {
-        this.el.focus();
-      }, 50);
-      
+    if (isActive) {      
       this.prepareLazyLoaded();
     }
   }
@@ -88,7 +83,6 @@ export class Tab implements ComponentInterface {
           'ion-page': component === undefined,
           'tab-hidden': !active,
         }}
-        tabIndex={!active ? '-1' : '0'}
       >
         <slot></slot>
       </Host>