Auto merge of #127028 - Nadrieril:fix-or-pat-expansion, r=matthewjasper

Fix regression in the MIR lowering of or-patterns

In rust-lang/rust#126553 I made a silly indexing mistake and regressed the MIR lowering of or-patterns. This fixes it.

r? `@compiler-errors` because I'd like this to be merged quickly 🙏

Author: bors