Fix URL for Checking out Chromium instructions.

Bug: 338521276
Change-Id: I1d807d73c2f13b3d84a73cce5154b4c53ea3a090
Test: N/A
diff --git a/docs/custom_vm.md b/docs/custom_vm.md
index b218a5e..57a1b0d 100644
--- a/docs/custom_vm.md
+++ b/docs/custom_vm.md
@@ -39,7 +39,7 @@
 First, check out source code from the ChromiumOS and Chromium projects.
 
 * Checking out ChromiumOS: https://www.chromium.org/chromium-os/developer-library/guides/development/developer-guide/
-* Checking out Chromium: https://g3doc.corp.google.com/chrome/chromeos/system_services_team/dev_instructions/g3doc/setup_checkout.md?cl=headless
+* Checking out Chromium: https://g3doc.corp.google.com/chrome/chromeos/system_services_team/dev_instructions/g3doc/setup_checkout.md?cl=head
 
 Important: When you are at the step “Set up gclient args” in the Chromium checkout instruction, configure .gclient as follows.