LLM Observability documentation fixes: Broken links, grammar, and spe…

…lling (microsoft#2995)

* update markdown hyperlinks to stable urls

* update notebook images and text

* re-write observability section

* Updated section

* update wording

* added newline

* update styling in image tags to be jsx compatible

* added text

* update link

* simplified text

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Co-authored-by: Braelyn Boynton <[email protected]>