appveyor: Leverage auto-retry to upload to S3
appveyor: Leverage auto-retry to upload to S3

This was recently implemented (appveyor/ci#1387) in response to one of our
feature requests, so let's take advantage of it! I'm going to optimistically
say...

Closes #39074

graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust