Fix curl shell examples which cause 400 Bad Request

What does this MR do and why?

Due to an redundant \, the original curl examples in Repository files API cause HTTP 400 error. The \ in single quote does not concatenate lines! It's a literal \ which is not wanted in POST data. This MR fixes the problem.

Screenshots or screen recordings

Before and after:

How to set up and validate locally

Run the curl example in the doc.

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