Auto merge of #119112 - Nadrieril:remove-target_blocks-hack, r=matthewjasper

match lowering: Remove the `make_target_blocks` hack

This hack was introduced 4 years ago in [`a1d0266` (#60730)](rust-lang/rust@a1d0266) to improve LLVM optimization time, specifically noticed in the `encoding` benchmark. Measurements today indicate it is no longer needed.

r? `@matthewjasper`

Author: bors