Prepare for merging from rust-lang/rust

The rustc-josh-sync Cronjob Bot · The rustc-josh-sync Cronjob Bot · commit b12f71178b10 · 2025-10-27T04:14:59.000Z
This updates the rust-version file to b1b464d.
diff --git a/src/doc/rustc-dev-guide/rust-version b/src/doc/rustc-dev-guide/rust-version
@@ -1 +1 @@
-4068bafedd8ba724e332a5221c06a6fa531a30d2
+b1b464d6f61ec8c4e609c1328106378c066a9729
