README: Update location of the test_planner code

It was moved to https://chromium.googlesource.com/chromiumos/infra/go,
but now lives in
https://chromium.googlesource.com/infra/infra/+/HEAD/go/src/infra/cros/cmd/test_plan_generator

BUG=b:234019083
TEST=None

Change-Id: Ifb9f8a32ae4a08a44472f9acbc27ef2a11ebfc13
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/test_planner/+/3668428
Tested-by: Nicholas Bishop <nicholasbishop@google.com>
Auto-Submit: Nicholas Bishop <nicholasbishop@google.com>
Reviewed-by: Dhanya Ganesh <dhanyaganesh@chromium.org>
Commit-Queue: Dhanya Ganesh <dhanyaganesh@chromium.org>
diff --git a/README.md b/README.md
index a33af14..5b771b1 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # test\_planner code has moved
 
-The test planner code has been relocated to the chromiumos/infra/go repo.
-See https://chromium.googlesource.com/chromiumos/infra/go
+The test planner code has been relocated to the infra/infra repo.
+See https://chromium.googlesource.com/infra/infra/+/HEAD/go/src/infra/cros/cmd/test_plan_generator
 
 This repo is effectively dead, but it should be kept in existence since
 older manifests may reference it.