dev-plugins: Correct missing @Inject annotation

The @Inject annotation is required on constructors that override
the InitStep.  The documentation erroneously omitted this annotation.

Change-Id: Ib551f03becf20fcbda703fe032db64aa1ef010d1

Documentation/dev-plugins.txt

diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index fdac6d3..2137767 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -283,6 +283,7 @@
     private final ConsoleUI ui;
     private final AllProjectsConfig allProjectsConfig;
 
+    @Inject
     public MyInitStep(@PluginName String pluginName, ConsoleUI ui,
         AllProjectsConfig allProjectsConfig) {
       this.pluginName = pluginName;