Improved readability of TensorFlow description.
@soosung80
@joefernandez

Why can't I add you two as reviewers? Hi @soosung80 / @joefernandez Can you please review this PR ? Thank you! So, Copybara doesn't want to merge the PR after it created the commit (87197a464c7cb21135ce66bcf861a92d465f20fc) for it. This is because you have synced it to master after it was imported in the internal system (was in the Piper area in the diagram below):

![life of a TF PR](https://user-images.githubusercontent.com/323199/229561784-0a2f5509-b731-493f-ad88-bad487688c8d.png)

As such, sadly, we'll need to manually close the PR.
Slightly altered the README file of TensorFlow to become more readable, and included a missing indefinite article in the same file.

![Screenshot 2023-03-14 at 18 46 42](https://user-images.githubusercontent.com/79566933/225123682-8941af51-33bd-4b59-889e-95c9b7c828b8.png)
