use a class private getter to decouple same methods usage

js/src/popover.js

@@ -19,7 +19,6 @@ const NAME = 'popover'
 const DATA_KEY = 'bs.popover'
 const EVENT_KEY = `.${DATA_KEY}`
 const CLASS_PREFIX = 'bs-popover'
-const BSCLS_PREFIX_REGEX = new RegExp(`(^|\\s)${CLASS_PREFIX}\\S+`, 'g')
 
 const Default = {
   ...Tooltip.Default,
@@ -124,21 +123,12 @@ class Popover extends Tooltip {
 
   // Private
 
-  _addAttachmentClass(attachment) {
-    this.getTipElement().classList.add(`${CLASS_PREFIX}-${this.updateAttachment(attachment)}`)
-  }
-
   _getContent() {
     return this._element.getAttribute('data-bs-content') || this._config.content
   }
 
-  _cleanTipClass() {
-    const tip = this.getTipElement()
-    const tabClass = tip.getAttribute('class').match(BSCLS_PREFIX_REGEX)
-    if (tabClass !== null && tabClass.length > 0) {
-      tabClass.map(token => token.trim())
-        .forEach(tClass => tip.classList.remove(tClass))
-    }
+  _getBasicClassPrefix() {
+    return CLASS_PREFIX
   }
 
   // Static