[DOCS][MINOR] Fixed a few typos in the Structured Streaming documentation

Fixed a few typos.

There is one more I'm not sure of:

```
        Append mode uses watermark to drop old aggregation state. But the output of a
        windowed aggregation is delayed the late threshold specified in `withWatermark()` as by
        the modes semantics, rows can be added to the Result Table only once after they are
```

Not sure how to change `is delayed the late threshold`.

Author: Seigneurin, Alexis (CONT) <Alexis.Seigneurin@capitalone.com>

Closes #17443 from aseigneurin/typos.