docs(Form): use new unified syntax for perf

src/form/test/__snapshots__/demo.spec.js.snap

@@ -76,14 +76,14 @@ exports[`renders demo correctly 1`] = `
                 <div role="checkbox" tabindex="0" aria-checked="false" class="van-checkbox van-checkbox--horizontal">
                   <div class="van-checkbox__icon van-checkbox__icon--square"><i class="van-icon van-icon-success">
                       <!----></i></div><span class="van-checkbox__label">
-          复选框 1
-        </span>
+            复选框 1
+          </span>
                 </div>
                 <div role="checkbox" tabindex="0" aria-checked="false" class="van-checkbox van-checkbox--horizontal">
                   <div class="van-checkbox__icon van-checkbox__icon--square"><i class="van-icon van-icon-success">
                       <!----></i></div><span class="van-checkbox__label">
-          复选框 2
-        </span>
+            复选框 2
+          </span>
                 </div>
               </div>
             </div>

src/form/test/props.spec.js

@@ -150,7 +150,9 @@ test('input-align prop', () => {
       <van-form input-align="right">
         <van-field />
         <van-field>
-          <div slot="input" />
+          <template #input>
+            <div />
+          </template>
         </van-field>
       </van-form>
     `,