fix arrow popover (#29115)

js/src/popover/popover.js

@@ -105,10 +105,6 @@ class Popover extends Tooltip {
     return this.getTitle() || this._getContent()
   }
 
-  addAttachmentClass(attachment) {
-    this.getTipElement().classList.add(`${CLASS_PREFIX}-${attachment}`)
-  }
-
   setContent() {
     const tip = this.getTipElement()
 
@@ -125,6 +121,10 @@ class Popover extends Tooltip {
     tip.classList.remove(ClassName.SHOW)
   }
 
+  _addAttachmentClass(attachment) {
+    this.getTipElement().classList.add(`${CLASS_PREFIX}-${attachment}`)
+  }
+
   // Private
 
   _getContent() {