Auto merge of #93719 - scottmcm:core-as-2021-everywhere, r=Mark-Simulacrum

Build libcore as 2021 in a few more places

The `Cargo.toml` has `edition = "2021"` (as of #92068), so that's what these command lines should use too.

Author: bors

core/Cargo.toml

@@ -6,6 +6,8 @@ repository = "https://github.com/rust-lang/rust.git"
 description = "The Rust Core Library"
 autotests = false
 autobenches = false
+# If you update this, be sure to update it in a bunch of other places too!
+# As of 2022, it was the ci/pgo.sh script and the core-no-fp-fmt-parse test.
 edition = "2021"
 
 [lib]