DEVPROD-8661 Document untracked branch tasks not having all expansions

docs/Project-Configuration/Project-Configuration-Files.md

@@ -777,14 +777,6 @@ Every task has some expansions available by default:
     the base commit is the PR base chosen by GitHub.
 -   `${github_commit}` is the commit hash of the commit that triggered
     the patch run
--   `${project}` is the project identifier the task belongs to
--   `${project_identifier}` is the project identifier the task belongs
-    to // we will be deprecating this, please use `${project}`
--   `${project_id}` is the project ID the task belongs to (note that for
-    later projects, this is the unique hash, whereas for earlier
-    projects this is the same as `${project}`. If you aren't sure which
-    you are, you can check using this API route:
-    `https://evergreen.mongodb.com/rest/v2/<project_id>`)
 -   `${branch_name}` is the name of the branch tracked by the
     project
 -   `${distro_id}` is name of the distro the task is running on
@@ -822,6 +814,17 @@ Every task has some expansions available by default:
 -   `${__project_aws_ssh_key_value}` is the unencrypted PEM encoded PKCS#1 private key 
     returned along with `${__project_aws_ssh_key_name}`.
 
+The following expansions are available unless a task was from an
+[untracked branch](Repo-Level-Settings.md#how-to-use-pr-testing-for-untracked-branches).
+
+-   `${project}` is the project identifier the task belongs to
+-   `${project_identifier}` is the project identifier the task belongs
+    to // we will be deprecating this, please use `${project}`
+-   `${project_id}` is the project ID the task belongs to (note that for
+    later projects, this is the unique hash, whereas for earlier
+    projects this is the same as `${project}`. If you aren't sure which
+    you are, you can use the [projects get route](../API/REST-V2-Usage#tag/projects/paths/~1projects~1%7Bproject_id%7D/get)).
+
 The following expansions are available if a task was triggered by an
 inter-project dependency: