Add copyartifact permission to tf-m-build-docs

We want to copy the docs into the parent job, so give copy artifact
permission to specific TF jobs.

Change-Id: I1bad4ff8f1097e4564af0979ffcccaa6890c74f8
diff --git a/tf-m-build-docs.yaml b/tf-m-build-docs.yaml
index f899cc6..8074854 100644
--- a/tf-m-build-docs.yaml
+++ b/tf-m-build-docs.yaml
@@ -16,6 +16,8 @@
       - build-discarder:
           days-to-keep: 15
           num-to-keep: 45
+      - copyartifact:
+          projects: "tf-m-nightly,tf-m-build-and-test"
     parameters:
       - string:
           name: 'GERRIT_REFSPEC'