Fix Buildifier version (#124)

"buildifier: true" has been deprecated by https://github.com/bazelbuild/continuous-integration/pull/542

.bazelci/presubmit.yml

diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index 6bdf62c..13a2227 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -108,4 +108,4 @@
     - "-//tests:analysis_test_e2e_test"
     - "-//tests:unittest_e2e_test"
 
-buildifier: true
+buildifier: latest