docs: improve Form demo (#9149)

src/picker/README.md

@@ -217,8 +217,8 @@ export default {
 ```html
 <van-field
   v-model="state.value"
+  is-link
   readonly
-  clickable
   label="City"
   placeholder="Choose City"
   @click="state.showPicker = true"

src/picker/README.zh-CN.md

@@ -241,8 +241,8 @@ export default {
 ```html
 <van-field
   v-model="state.value"
+  is-link
   readonly
-  clickable
   label="城市"
   placeholder="选择城市"
   @click="state.showPicker = true"

src/picker/demo/index.vue

@@ -49,8 +49,8 @@
   <demo-block card v-if="!isWeapp" :title="t('withPopup')">
     <van-field
       v-model="fieldValue"
+      is-link
       readonly
-      clickable
       :label="t('city')"
       :placeholder="t('chooseCity')"
       @click="onClickField"

src/picker/test/__snapshots__/demo.spec.ts.snap

@@ -692,6 +692,8 @@ exports[`should render demo and match snapshot 1`] = `
         >
       </div>
     </div>
+    <i class="van-badge__wrapper van-icon van-icon-arrow van-cell__right-icon">
+    </i>
   </div>
   <transition-stub>
   </transition-stub>