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)