Auto merge of #43884 - kennytm:fix-43881-do-not-test-i586-msvc, r=alexcrichton
Auto merge of #43884 - kennytm:fix-43881-do-not-test-i586-msvc, r=alexcrichton

Stop testing `i586-pc-windows-msvc` on AppVeyor.

Fixes #43881. Reduces AppVeyor test time back to ~2 hours on average.

The i586 libstd was never tested before Aug 13th, so this PR brings the situation back to the previous status-quo.

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