[dbt-snowflake] Expose ocsp_fail_open as a parameter

[jcrobak]

resolves #793

Problem

The setting ocsp_fail_open, which is a parameter to the snowflake-connector-python, is not currently exposed in the dbt-snowflake adapter.

Solution

We only pass along the parameter when it's set so that we can defer to the builtin default of the snowflake-connector-python (historically the default has changed between versions).

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

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