Add branch to infra configs, per go/flutter-self-service-branches.

.ci.yaml

diff --git a/.ci.yaml b/.ci.yaml
index d537efd..9f94624 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -12,6 +12,7 @@
   - beta
   - stable
   - flutter-2.7-candidate.5
+  - fuchsia_f7
 
 platform_properties:
   linux: