fix type imports

Author: yyx990803

src/directives/if.ts

@@ -1,7 +1,7 @@
 import { Block } from '../block'
 import { evaluate } from '../eval'
 import { checkAttr } from '../utils'
-import { Context } from '../walk'
+import { Context } from '../context'
 
 interface Branch {
   exp?: string | null

src/directives/index.ts

@@ -1,4 +1,4 @@
-import { Context } from '../walk'
+import { Context } from '../context'
 import { effect as rawEffect } from '@vue/reactivity'
 import { bind } from './bind'
 import { on } from './on'