Doc: add some missing description for ssl_mode and server_ca_mode.

[feng-zhe]

Add some missing description for ssl_mode and server_ca_mode. Related issue hashicorp/terraform-provider-google#19711.

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-))
google-beta provider: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-))

[SarahFrench]

Hi, thanks for your PR!

In the original issue the author wants the detail present here in the old docs to be reintroduced. Could you please add those details into your PR too?

[SarahFrench]

Are any of the values here Beta-only? If not we should link to the GA version of the API documentation to avoid any potential confusion

[feng-zhe]

We cannot reintroduce the previous details because the require_ssl field has been deprecated in 6.0.0. So we only need to describe the valid values of ssl_mode.

I've updated the API version to v1. Thanks.

[SarahFrench]

Ah, thanks, I missed that that was a factor!

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-))
google-beta provider: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-))