【CocoaPods】pod initでエラー：Unknown object version.の解決方法

久々にpod initしたらエラーになっちゃいました。。その原因と解決方法をここに記載しておきます。

Contents

エラー内容
原因
解決方法
まとめ

エラー内容

pod initをしたら、以下のようなエラーが表示された。

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### Command

```
/usr/local/bin/pod init
```

### Report

* What did you do?

* What did you expect to happen?

* What happened instead?


### Stack

```
   CocoaPods : 1.10.1
        Ruby : ruby 2.6.3p62 (2019-04-16 revision 67580) [universal.x86_64-darwin20]
    RubyGems : 3.0.3
        Host : macOS 11.5.2 (20G95)
       Xcode : 13.0 (13A233)
         Git : git version 2.30.1 (Apple Git-130)
Ruby lib dir : /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib
Repositories : trunk - CDN - https://cdn.cocoapods.org/
```

### Plugins

```
cocoapods-deintegrate : 1.0.4
cocoapods-plugins     : 1.0.0
cocoapods-search      : 1.0.0
cocoapods-stats       : 1.1.0
cocoapods-trunk       : 1.5.0
cocoapods-try         : 1.2.0
```

### Error

```
RuntimeError - [Xcodeproj] Unknown object version.
/Library/Ruby/Gems/2.6.0/gems/xcodeproj-1.19.0/lib/xcodeproj/project.rb:227:in `initialize_from_file'
/Library/Ruby/Gems/2.6.0/gems/xcodeproj-1.19.0/lib/xcodeproj/project.rb:112:in `open'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command/init.rb:41:in `validate!'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:333:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/bin/pod:55:in `<top (required)>'
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `<main>'
```

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[!] Oh no, an error occurred.

Search for existing GitHub issues similar to yours:
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