fix(upgrade): correctly update version range in package.json (#4546)

Author: haoqunjiang

packages/@vue/cli/__tests__/Upgrader.spec.js

@@ -34,6 +34,9 @@ test('upgrade: plugin-babel v3.5', async () => {
   expect(updatedPkg.dependencies).toHaveProperty('core-js')
 
   expect(logs.log.some(([msg]) => msg.match('core-js has been upgraded'))).toBe(true)
+
+  // should have updated the version range in package.json
+  expect(updatedPkg.devDependencies['@vue/cli-plugin-babel']).not.toMatch('3.5.3')
 })
 
 test('upgrade: plugin-babel with core-js 2', async () => {

packages/@vue/cli/lib/Upgrader.js

@@ -101,6 +101,8 @@ module.exports = class Upgrader {
     log(`Upgrading ${packageName} from ${installed} to ${targetVersion}`)
     await this.pm.upgrade(`${packageName}@^${targetVersion}`)
 
+    // the cached `pkg` field won't automatically update after running `this.pm.upgrade`
+    this.pkg[depEntry][packageName] = `^${targetVersion}`
     await this.runMigrator(packageName, { installed })
   }