Update build/release documentation with new API/WAR commands

Change Ia246000f8 introduced new scripts to build and deploy
the API and WAR, but some documentation updates were missed.

Bug: Issue 4479
Change-Id: If5d4ce2a351463e9ddf88d3765b59955ce23ce54
diff --git a/Documentation/dev-build-plugins.txt b/Documentation/dev-build-plugins.txt
index 2c04d17..13071df 100644
--- a/Documentation/dev-build-plugins.txt
+++ b/Documentation/dev-build-plugins.txt
@@ -36,7 +36,7 @@
 * build and install `SNAPSHOT` version of plugin API in local Maven repository:
 
 ----
-buck build api_install
+./tools/maven/api.sh install
 ----
 
 === Exception 2: