Prepare for merging from rust-lang/rust

The rustc-josh-sync Cronjob Bot · The rustc-josh-sync Cronjob Bot · commit 11153451845f · 2025-07-24T04:15:31.000Z
This updates the rust-version file to efd420c.
diff --git a/src/doc/rustc-dev-guide/rust-version b/src/doc/rustc-dev-guide/rust-version
@@ -1 +1 @@
-460259d14de0274b97b8801e08cb2fe5f16fdac5
+efd420c770bb179537c01063e98cb6990c439654
