test: fix slow tests on next branch (#4076)

Author: erickzhao

packages/api/core/spec/fixture/custom_init/index.js

@@ -4,7 +4,7 @@ const baseTemplate = require('@electron-forge/template-base').default;
 const fs = require('fs-extra');
 
 module.exports = {
-  requiredForgeVersion: '>= 6.0.0-beta.1',
+  requiredForgeVersion: '>= 8.0.0-alpha.0',
   dependencies: [...baseTemplate.dependencies, 'debug'],
   devDependencies: [...baseTemplate.devDependencies, 'lodash'],
   initializeTemplate: async (directory) => {