Cleaned transcript for Austin video "Intro to Prob. Programming with PyMC" (#233)

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Cleaned the entire transcript by adding appropriate punctuations, fixing typos, and correcting formatting inconsistencies.

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* Update about/probabilistic_programming_with_pymc/transcript.md

* Update about/probabilistic_programming_with_pymc/transcript.md

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Co-authored-by: Reshama Shaikh <reshama.stat@gmail.com>

Author: anushatomar13