fix: less variable bug

Author: yaoleyaotouoO

docs/demos/index.vue

@@ -4,7 +4,7 @@
       <SchemaStringField
         name="input"
         x-component="Input"
-        :x-component-props="{ label: '输入框', placeholder: '请输入' }"
+        :x-component-props="{ label: '输入框', placeholder: '请输入...' }"
       />
 
       <SchemaStringField

packages/components/src/__builtins__/styles/common.less

@@ -1,2 +1 @@
-@formily-prefix: 'formily-vant';
-@namespace: 'vant';
+@formily-prefix: formily-vant;