Clarify default value for `ocspStaplingRefreshPeriodSecs` and clarify its behavior if not set

Description

Hi Docs Team,

MongoDB Server v. 4.4.X introduces OCSP stapling functionality, however `ocspStaplingRefreshPeriodSecs` does not describe its default value.

As I can see it has default defined as not set (`-1`) in ssl_parameters.idl#L75-L83, it would be nice to clarify OCSP stapling functionality if `ocspStaplingRefreshPeriodSecs` is not set (i.e. if it is with default value).

Can you please have a look?

CC: @andrew.feierabend

Thanks in advance,
Alexey

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