Project-Goals-2025-April-Update: Broken link to parallel frontend issue list

[comex]

In Project-Goals-2025-April-Update.md, there is a link to:

https://github.com/rust-lang/rust/labels/WG-compiler-parallel

but this label doesn't exist. Perhaps it should link to:

https://github.com/rust-lang/rust/labels/A-parallel-compiler

[comex]

(cc @SparrowLii since this text originally comes from their comments in the rust-project-goals issue.)

[senekor]

Hm, there's also a label WG-compiler-performance.