Documentation: Refactor to match other plugin documentation

Replace hard-coded command for plugin in-tree build.

Change-Id: Ic7c90441e7bf158da2544f10c8b6d100c31a5a01
diff --git a/src/main/resources/Documentation/build.md b/src/main/resources/Documentation/build.md
index 9bb02c2..5cc21c0 100644
--- a/src/main/resources/Documentation/build.md
+++ b/src/main/resources/Documentation/build.md
@@ -11,7 +11,7 @@
 Then issue
 
 ```
-  bazel build plugins/changemessage
+  bazel build plugins/@PLUGIN@
 ```
 
 in the root of Gerrit's source tree to build
@@ -19,7 +19,7 @@
 The output is created in
 
 ```
-  bazel-bin/plugins/changemessage/changemessage.jar
+  bazel-bin/plugins/@PLUGIN@/@PLUGIN@.jar
 ```
 
 This project can be imported into the Eclipse IDE.