Fix integration test TestDocCompletion (#1180)

PR #1177 introduced a new .md file in docs/diagrams. However, this file
is a guide to how to use the diagram tooling rather than adsys
documentation, so we need to ignore that directory as well in the test
checks.

cmd/adsysd/integration_tests/adsysctl_doc_test.go

@@ -120,7 +120,8 @@ func TestDocCompletion(t *testing.T) {
 				if d.IsDir() ||
 					strings.HasPrefix(path, filepath.Join(docsDir, "reuse")) ||
 					strings.HasPrefix(path, docsDir+"/.") ||
-					strings.HasPrefix(path, filepath.Join(docsDir, "reference", "policies")) {
+					strings.HasPrefix(path, filepath.Join(docsDir, "reference", "policies")) ||
+					strings.HasPrefix(path, filepath.Join(docsDir, "diagrams")) {
 					return nil
 				}
 				if !strings.HasSuffix(d.Name(), ".md") {