Add project-group-structure plugin to the check pipeline

Depends-On: https://gerrit-review.googlesource.com/273732
Change-Id: I5ae4b181cfc8818d193f9c8cbf14407081403b2e

zuul.d/projects.yaml

diff --git a/zuul.d/projects.yaml b/zuul.d/projects.yaml
index 0a7ebdb..74da6d4 100644
--- a/zuul.d/projects.yaml
+++ b/zuul.d/projects.yaml
@@ -99,6 +99,12 @@
         - gerrit-plugin-build
 
 - project:
+    name: plugins/project-group-structure
+    check:
+      jobs:
+        - gerrit-plugin-build
+
+- project:
     name: plugins/reviewers
     check:
       jobs: