Fix failing BuildExamplePluginsIT test

plugins/examples/custom-suggester/build.gradle

@@ -23,6 +23,8 @@ esplugin {
     name 'custom-suggester'
     description 'An example plugin showing how to write and register a custom suggester'
     classname 'org.elasticsearch.example.customsuggester.CustomSuggesterPlugin'
+    licenseFile rootProject.file('licenses/APACHE-LICENSE-2.0.txt')
+    noticeFile rootProject.file('NOTICE.txt')
 }
 
 integTestCluster {