fix(autocomplete): it's abount click clear button and the drop-down box does not appear

fix #21377,fix #19050, fix #18970

examples/docs/zh-CN/input.md

@@ -549,6 +549,7 @@ export default {
   v-model="state"
   :fetch-suggestions="querySearchAsync"
   placeholder="请输入内容"
+  clearable
   @select="handleSelect"
 ></el-autocomplete>
 <script>

packages/autocomplete/src/autocomplete.vue

@@ -195,6 +195,7 @@
           this.suggestions = [];
           return;
         }
+        this.activated = true;
         this.debouncedGetData(value);
       },
       handleChange(value) {