[move-stdlib] fix vector docs

[geometryolife]

Motivation

Fix typos in the vector.

Have you read the Contributing Guidelines on pull requests?

Yes

[geometryolife]

I’d like to ask how to write test cases for documents.
I tried to modify this for the first time, and I didn’t know what to do.
@sblackshear

[leofisG]

You need to regenerate the documentation. Do script/check_pr.sh -d.

[geometryolife]

You need to regenerate the documentation. Do script/check_pr.sh -d.

Thank you very much for your help, I learned!