perfetto-ci: only show results for "master" branch

Not tested besides doing a manual fetch from the new url.

Change-Id: I62f279e3e40ae05266f20cace6d82a855adc68e6
diff --git a/infra/ci/frontend/static/script.js b/infra/ci/frontend/static/script.js
index 18c36bf..383010d 100644
--- a/infra/ci/frontend/static/script.js
+++ b/infra/ci/frontend/static/script.js
@@ -562,7 +562,7 @@
 async function fetchGerritCLs() {
   console.log('Fetching CL list from Gerrit');
   let uri = '/gerrit/changes/?-age:7days';
-  uri += '+-is:abandoned&o=DETAILED_ACCOUNTS&o=CURRENT_REVISION';
+  uri += '+-is:abandoned+branch:master&o=DETAILED_ACCOUNTS&o=CURRENT_REVISION';
   const response = await fetch(uri);
   state.gerritCls = [];
   if (response.status !== 200) {