mention git switch alongside git checkout for moving HEAD

where that makes more sense than a replacement

Author: das-g

book/10-git-internals/sections/refs.asc

@@ -84,7 +84,7 @@ $ cat .git/HEAD
 ref: refs/heads/master
 ----
 
-If you run `git checkout test`, Git updates the file to look like this:
+If you run `git switch test` or `git checkout test`, Git updates the file to look like this:
 
 [source,console]
 ----
@@ -205,5 +205,5 @@ ca82a6dff817ec66f44342007202690a93763949
 ----
 
 Remote references differ from branches (`refs/heads` references) mainly in that they're considered read-only.
-You can `git checkout` to one, but Git won't symbolically reference HEAD to one, so you'll never update it with a `commit` command.
+You can `git checkout` (or `git switch --detach`) to one, but Git won't symbolically reference HEAD to one, so you'll never update it with a `commit` command.
 Git manages them as bookmarks to the last known state of where those branches were on those servers.