Align the recommended buildifier version with CI's

The recently merged CI change [1] upgraded the buildifier version for CI
to 4.0.0. Recommend the latter now in the documentation, consistently.

[1] https://gerrit-review.googlesource.com/c/gerrit-ci-scripts/+/296133

Change-Id: I0d2b3aaf34229235df3ef0b2beaa9508ae1725d9
diff --git a/Documentation/dev-crafting-changes.txt b/Documentation/dev-crafting-changes.txt
index d71d227..0f2a973 100644
--- a/Documentation/dev-crafting-changes.txt
+++ b/Documentation/dev-crafting-changes.txt
@@ -146,7 +146,7 @@
 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 3.5.0). Unused dependencies are found and removed using the
+tool (version 4.0.0). Unused dependencies are found and removed using the
 link:https://github.com/bazelbuild/buildtools/tree/master/unused_deps[`unused_deps`]
 build tool, a sibling of `buildifier`.