OAuth Configuration Documentation: "client_secret" is "client_secrets" - adapt documentation

**Expected Behavior**

The documentation (OAuth configuration) matches the tool (version 4.2.0).

**Actual Behavior**

The documentation for OAuth does not match the config keys in 4.2.0:

The documentation at https://github.com/adobe/aio-cli-plugin-cloudmanager?tab=readme-ov-file#setup-for-oauth-integration mentions that the OAuth config has a key "client_secret", but the field is now called "client_secrets" (for OAuth only) and has become a list property, see e.g. here: https://github.com/adobe/aio-cli-plugin-cloudmanager/blob/main/e2e/e2e.js#L72

**Reproduction Scenario, Platform, and Version**

Version 4.2.0

**Steps to Reproduce**

Setup aio cli-cloudmanager using OAuth according to documentation https://github.com/adobe/aio-cli-plugin-cloudmanager?tab=readme-ov-file#setup-for-oauth-integration
You will get an HTTP 400 (parameter client_secrets missing)

从仓库 README 中的 OAuth 配置部分开始，并将其中记录的键与版本 4.2.0 的 e2e/e2e.js 第 72 行附近的内容进行比较。更新文档，使 OAuth 配置与工具一致，然后验证设置步骤不再引用缺失的参数。

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