Add Bazel to downstream projects in the testing org.

Otherwise it will not have a "last green" status.
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 6ffc1e7..919c1fd 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -364,11 +364,16 @@
 }
 
 DOWNSTREAM_PROJECTS_TESTING = {
+    "Bazel": {
+        "git_repository": "https://github.com/bazelbuild/bazel.git",
+        "http_config": "https://raw.githubusercontent.com/bazelbuild/bazel/master/.bazelci/postsubmit.yml",
+        "pipeline_slug": "bazel-bazel",
+    },
     "Bazelisk": {
         "git_repository": "https://github.com/bazelbuild/bazelisk.git",
         "http_config": "https://raw.githubusercontent.com/bazelbuild/bazelisk/master/.bazelci/config.yml",
         "pipeline_slug": "bazelisk",
-    }
+    },
 }
 
 DOWNSTREAM_PROJECTS = {