Update books

ehuss · ehuss · commit 8dc09e1d040f · 2021-04-28T11:28:57.000-07:00
diff --git a/src/doc/book b/src/doc/book
@@ -1 +1 @@
-Subproject commit b54090a99ec7c4b46a5203a9c927fdbc311bb1f5
+Subproject commit 50dd06cb71beb27fdc0eebade5509cdcc1f821ed
diff --git a/src/doc/reference b/src/doc/reference
@@ -1 +1 @@
-Subproject commit e1abb17cd94cd5a8a374b48e1bc8134a2208ed48
+Subproject commit d23f9da8469617e6c81121d9fd123443df70595d
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
@@ -1 +1 @@
-Subproject commit c80f0b09fc15b9251825343be910c08531938ab2
+Subproject commit e0a721f5202e6d9bec0aff99f10e44480c0da9e7
diff --git a/src/doc/rustc-dev-guide b/src/doc/rustc-dev-guide
@@ -1 +1 @@
-Subproject commit a9bd2bbf31e4f92b5d3d8e80b22839d0cc7a2022
+Subproject commit e72b43a64925ce053dc7830e21c1a57ba00499bd
