[BugFix] Fix topk_softmax assert

[ProExpertProg]

Essential Elements of an Effective PR Description Checklist

• [x] The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• [x] The test plan, such as providing test command.
• [x] The test results, such as pasting the results comparison before and after, or e2e results
• [ ] (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Fix the assert (only compiled in debug mode) and change it to a TORCH_CHECK. Introduced in #18434.

Test Plan

CI

Test Result

(Optional) Documentation Update

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[varun-sundar-rabindranath]

Thanks for the fix @ProExpertProg 🙌

[DarkLight1337]

Can you merge from main to see if the CI failures can be resolved?