Upgrade buildifier to 0.22.0

Change-Id: I46c05447c2aedc6a5d961fdd611760fb552176cb
diff --git a/Documentation/dev-contributing.txt b/Documentation/dev-contributing.txt
index 6b51cbe..e916c2a 100644
--- a/Documentation/dev-contributing.txt
+++ b/Documentation/dev-contributing.txt
@@ -155,7 +155,7 @@
 link:https://github.com/google/google-java-format[`google-java-format`]
 tool (version 1.7), and to format Bazel BUILD, WORKSPACE and .bzl files the
 link:https://github.com/bazelbuild/buildtools/tree/master/buildifier[`buildifier`]
-tool (version 0.20.0).
+tool (version 0.22.0).
 These tools automatically apply format according to the style guides; this
 streamlines code review by reducing the need for time-consuming, tedious,
 and contentious discussions about trivial issues like whitespace.