Fix typo and grammar in introduction_to_deep_research_api.ipynb

[leohpark]

Fix two small typos on one sentence of this guide.

Summary

Original sentence is missing verb and does not contain proper formatting in referring to "detailed"

Motivation

Why are these changes necessary? How do they improve the cookbook?

Clarifies grammar, and specifies that "detailed" is a user provided parameter

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[leohpark]

commenting to unstale?