[MINOR][DOC] Use standard quotes instead of "curly quote" marks from Mac in...

[MINOR][DOC] Use standard quotes instead of "curly quote" marks from Mac in structured streaming programming guides

## What changes were proposed in this pull request?

This PR fixes curly quotes (`“` and `”` ) to standard quotes (`"`).

This will be a actual problem when users copy and paste the examples. This would not work.

This seems only happening in `structured-streaming-programming-guide.md`.

## How was this patch tested?

Manually built.

This will change some examples to be correctly marked down as below:

![2016-08-23 3 24 13](https://cloud.githubusercontent.com/assets/6477701/17882878/2a38332e-694a-11e6-8e84-76bdb89151e0.png)

to

![2016-08-23 3 26 06](https://cloud.githubusercontent.com/assets/6477701/17882888/376eaa28-694a-11e6-8b88-32ea83997037.png)

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #14770 from HyukjinKwon/minor-quotes.