fix: added missing import of the Cheerio type (fix #1526)

Author: Sergei Koshel

packages/server-test-utils/types/index.d.ts

@@ -1,5 +1,6 @@
 import Vue, { VNodeData, ComponentOptions, FunctionalComponentOptions, Component } from 'vue'
 import { DefaultProps, PropsDefinition } from 'vue/types/options'
+import * as Cheerio from 'cheerio'
 
 /**
  * Utility type to declare an extended Vue constructor