Rollup merge of #65448 - eddyb:codegen-box-less-special, r=oli-obk
Rollup merge of #65448 - eddyb:codegen-box-less-special, r=oli-obk

rustc_codegen_ssa: remove some unnecessary Box special-casing.

Could help simplify #60900.

r? @nikomatsakis

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