NO-SNOW: Disable flaky AI tests for a while.

[sfc-gh-jrose]

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

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
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   • If adding any arguments to public Snowpark APIs or creating new public Snowpark APIs, I acknowledge that I have ensured my changes include AST support. Follow the link for more information: AST Support Guidelines

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

This PR marks doctests for the dataframe ai functions as a non-strict xfail for a while due to some infra flakes that they are having. This will unblock a few changes for release.