Fix capacity comparison in reserve
Fix capacity comparison in reserve

You can otherwise end up in a situation where you don't actually resize
but still call into handle_cap_increase which then corrupts head/tail.

Closes #44800

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