unityにfirebaseを入れた際にビルドが通らない

前提・実現したいこと

unityでfirebaseを使用したい
firebaseの公式の手順に沿ってunityにfirebaseを入れ、iosでビルドしようとした際に以下のようなエラーが発生します。
このエラーを解消してビルドを通したいです。よろしくお願いいたします。

発生している問題・エラーメッセージ

iOS framework addition failed due to a CocoaPods installation failure. This will will likely result in an non-functional Xcode project.

After the failure, "pod repo update" was executed and succeeded. "pod install" was then attempted again, and still failed. This may be due to a broken CocoaPods installation. See: https://guides.cocoapods.org/using/troubleshooting.html for potential solutions.

pod install output:

Analyzing dependencies
[!] CocoaPods could not find compatible versions for pod "GoogleUtilities/SwizzlerTestHelpers":
  In Podfile:
    GoogleUtilities (= 5.2.0) was resolved to 5.2.0, which depends on
      GoogleUtilities/SwizzlerTestHelpers (= 5.2.0)

None of your spec sources contain a spec satisfying the dependency: `GoogleUtilities/SwizzlerTestHelpers (= 5.2.0)`.

You have either:
 * out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
 * mistyped the name or version.
 * not added the source repo that hosts the Podspec to your Podfile.

Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default.





pod repo update output:

Updating spec repo `master`



UnityEngine.Debug:LogError(Object)
Google.Logger:Log(String, LogLevel) (at Z:/tmp/tmp.MFNLcXgkvt/third_party/unity/unity_jar_resolver/source/VersionHandlerImpl/src/Logger.cs:103)
Google.IOSResolver:Log(String, Boolean, LogLevel) (at Z:/tmp/tmp.2Lme60LA56/third_party/unity/unity_jar_resolver/source/IOSResolver/src/IOSResolver.cs:967)
Google.IOSResolver:OnPostProcessInstallPods(BuildTarget, String) (at Z:/tmp/tmp.2Lme60LA56/third_party/unity/unity_jar_resolver/source/IOSResolver/src/IOSResolver.cs:2209)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

該当のソースコード

podfile
1source 'https://github.com/CocoaPods/Specs.git'
2source 'https://github.com/CocoaPods/Specs'
3platform :ios, '9.0'
4
5target 'Unity-iPhone' do
6  pod 'Firebase/Analytics', '6.3.0'
7  pod 'Firebase/Core', '6.3.0'
8  pod 'Google-Mobile-Ads-SDK', '~> 7.41'
9  pod 'GoogleUtilities', '5.2.0'
10end
11

試したこと

pod repo updateを行ったあと、pod installをしましたが同様のエラー内容でした。
同じようなエラー内容の記事を見つけたので以下のサイトを参考にしましたが、エラーが消えませんでした。
https://qiita.com/ippo/items/9cf708343769329b9fb5