Update rust-lang/book.

nnethercote · nnethercote · commit ab161d1f5dee · 2023-11-04T08:50:25.000+11:00
To 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb, for this commit: - Prepare for removal of compiler plugin support. (rust-lang/book#3764)
diff --git a/src/doc/book b/src/doc/book
@@ -1 +1 @@
-Subproject commit 3dca2fc50b922a8efb94903b9fee8bb42ab48f38
+Subproject commit 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb
