[test] add lucene expressions jar as test dependency

REST tests that use expressions as the script language requires the
lucene-expressions library to be loaded.

Original commit: elastic/x-pack-elasticsearch@c0f2b8a4b2

pom.xml

@@ -73,6 +73,12 @@
             <version>${lucene.maven.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.apache.lucene</groupId>
+            <artifactId>lucene-expressions</artifactId>
+            <version>${lucene.maven.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.elasticsearch</groupId>
             <artifactId>elasticsearch</artifactId>