Prepare v0.4.0-rc.0

Author: dhardy

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "getrandom"
-version = "0.3.4"
+version = "0.4.0-rc.0"
 edition = "2024"
 rust-version = "1.85" # Sync tests.yml and README.md.
 authors = ["The Rand Project Developers"]