Bump Dependency Versions

**Describe the solution you'd like**
Ensure that any dependencies, such as rexml, are up-to-date.

**Describe alternatives you've considered**
We could, perhaps, leave dependencies as-is. Given the time since last update, this is probably not desirable.

**Additional context**
Dependabot opened a [version bump PR](https://github.com/google/GoogleSignIn-iOS/pull/468) many moons ago. I closed it in order to clear out stale branches.

首先检查仓库的依赖配置和已关闭的版本更新 PR #468，特别注意 issue 中提到的 rexml 依赖。项目的依赖已更新到最新状态，并且由此产生的依赖变更已在没有回归的情况下完成验证，即表示完成。

由索引模型根据 Issue 内容生成。