fix(challenges): Change of text in Introduction to the basic node a
fix(challenges): Change of text in Introduction to the basic node a

Text was not getting changed going from step 1 to step 2 because ul
cannot be child node of p tag so I changed p tag to div in Introduction
to the basic node and express challenges. For ref.
https://stackoverflow.com/questions/10601345/ul-element-can-never-be-a-child-of-p-element

BREAKING CHANGE: Changed p tag to div tag in Step.jsx

Closes #15796

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