Update plugins for 2016.3.1.

2016.2.4 is still "intellij-latest".

MOE_MIGRATED_REVID=142804141
diff --git a/idea_plugin/google-java-format.iml b/idea_plugin/google-java-format.iml
index a5cd516..dfcd8e0 100644
--- a/idea_plugin/google-java-format.iml
+++ b/idea_plugin/google-java-format.iml
@@ -5,6 +5,8 @@
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/com/google/googlejavaformat/intellij/v2016_3" packagePrefix="com.google.googlejavaformat.intellij.v2016_3" isTestSource="false" />
+      <excludeFolder url="file://$MODULE_DIR$/src/com/google/googlejavaformat/intellij/v2016_2" />
       <sourceFolder url="file://$MODULE_DIR$/resources" type="java-resource" />
       <sourceFolder url="file://$MODULE_DIR$/test" isTestSource="true" />
     </content>