Form: fix a typo in docs (#10778)

examples/docs/en-US/form.md

@@ -639,7 +639,7 @@ This example shows how to customize your own validation rules to finish a two-fa
     label="Email"
     :rules="[
       { required: true, message: 'Please input email address', trigger: 'blur' },
-      { type: 'email', message: 'Please input correct email address', trigger: 'blur,change' }
+      { type: 'email', message: 'Please input correct email address', trigger: ['blur', 'change'] }
     ]"
   >
     <el-input v-model="dynamicValidateForm.email"></el-input>

examples/docs/es/form.md

@@ -640,7 +640,7 @@ Este ejemplo muestra cómo personalizar sus propias reglas de validación para f
     label="Email"
     :rules="[
       { required: true, message: 'Please input email address', trigger: 'blur' },
-      { type: 'email', message: 'Please input correct email address', trigger: 'blur,change' }
+      { type: 'email', message: 'Please input correct email address', trigger: ['blur', 'change'] }
     ]"
   >
     <el-input v-model="dynamicValidateForm.email"></el-input>

examples/docs/zh-CN/form.md

@@ -627,7 +627,7 @@ W3C 标准中有如下[规定](https://www.w3.org/MarkUp/html-spec/html-spec_8.h
     label="邮箱"
     :rules="[
       { required: true, message: '请输入邮箱地址', trigger: 'blur' },
-      { type: 'email', message: '请输入正确的邮箱地址', trigger: 'blur,change' }
+      { type: 'email', message: '请输入正确的邮箱地址', trigger: ['blur', 'change'] }
     ]"
   >
     <el-input v-model="dynamicValidateForm.email"></el-input>