Autocomplete: fix suggestion error when textarea (#18478)

packages/autocomplete/src/autocomplete-suggestions.vue

@@ -60,7 +60,7 @@
 
     mounted() {
       this.$parent.popperElm = this.popperElm = this.$el;
-      this.referenceElm = this.$parent.$refs.input.$refs.input;
+      this.referenceElm = this.$parent.$refs.input.$refs.input || this.$parent.$refs.input.$refs.textarea;
       this.referenceList = this.$el.querySelector('.el-autocomplete-suggestion__list');
       this.referenceList.setAttribute('role', 'listbox');
       this.referenceList.setAttribute('id', this.id);