Update keypair.py

[emilhe]

Please answer these questions before submitting your pull requests. Thanks!

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-744534: prepare() gets args, but supports only kwargs #1439

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am modifying authorization mechanisms
   • I am adding new credentials
   • I am modifying OCSP code
   • I am adding a new dependency

3. Please describe how your code solves the related issue.

   The error occurs because the prepare function expect user/account arguments to be keyword arguments, but they are passed as positional argument. This PR fixes the issue by passing them as keyword arguments instead.

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[emilhe]

I have read the CLA Document and I hereby sign the CLA

[sfc-gh-aling]

accompanying PR for testing: #1442