docs: fix type for retryCodes

[mkls]

Fixes misleading documentation

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here (e.g. I signed it!) and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

[mkls]

I signed it!

[googlebot]

CLAs look good, thanks!

[alexander-fenster]

It's definitely an array of numbers, so approved - but the problem is, I don't believe we actually use these JsDoc-style comments anywhere for now. May I ask what was the use case that made you fix this? ('Just wanted to fix it' is a perfectly valid answer, I'm just curious if there could be other reasons)

[mkls]

I was trying to change retry setting for @google-cloud/pubsub and the documentation for changing these (https://cloud.google.com/nodejs/docs/reference/pubsub/0.23.x/v1.PublisherClient#publish) eventually leads to http://googleapis.github.io/gax-nodejs/global.html#RetryOptions.
I figured this is an auto generated documentation, and changing this jsdoc comments would fix it.

[alexander-fenster]

Thank you! It makes perfect sense then. I didn't realize those jsdoc comments are used in the dependent libraries.

(I'll make the CI work and will merge this one)