doc: Remove pypi.<name>.ca_certs configuration option from docs (#2044)

This config option does not exist.

docs/docs/reference/configuration.md

@@ -59,7 +59,6 @@ The following configuration items can be retrieved and modified by [`pdm config`
 | `pypi.<name>.username`            | The username to access custom source                                      |                                                                       | Yes                  |                           |
 | `pypi.<name>.password`            | The password to access custom source                                      |                                                                       | Yes                  |                           |
 | `pypi.<name>.type`                | `find_links`                                                              | `index`                                                               | `index`              | Yes                       |  |
-| `pypi.<name>.ca_certs`            | Path to a PEM-encoded CA cert bundle (used for server cert verification)  | The CA certificates from [certifi](https://pypi.org/project/certifi/) | No                   |                           |
 | `pypi.<name>.verify_ssl`          | Verify SSL certificate when query custom source                           | `True`                                                                | Yes                  |                           |
 | `strategy.save`                   | Specify how to save versions when a package is added                      | `minimum`(can be: `exact`, `wildcard`, `minimum`, `compatible`)       | Yes                  |                           |
 | `strategy.update`                 | The default strategy for updating packages                                | `reuse`(can be : `eager`)                                             | Yes                  |                           |