Fix typo in extra packages building

Change-Id: I86a12ece2df472fc9e050a7094edd6ca3b2e62a5
diff --git a/jenkins/client/job/debian/packages/extra.yml b/jenkins/client/job/debian/packages/extra.yml
index fc797a5..b7de941 100644
--- a/jenkins/client/job/debian/packages/extra.yml
+++ b/jenkins/client/job/debian/packages/extra.yml
@@ -154,7 +154,7 @@
                 project:
                   debian/{{package}}:
                     branches:
-                      - {{branch}}
+                      - "{{branch}}"
                 message:
                   build_successful: "Build successful"
                   build_unstable: "Build unstable"