[DOCS][SS] fix structured streaming python example

## What changes were proposed in this pull request?

- SS python example: `TypeError: 'xxx' object is not callable`
- some other doc issue.

## How was this patch tested?

Jenkins.

Author: uncleGen <hustyugm@gmail.com>

Closes #17257 from uncleGen/docs-ss-python.

(cherry picked from commit e29a74d5)
Signed-off-by: Sean Owen <sowen@cloudera.com>