Fix DynaTableRf sample wrt servlet-api version

Jetty now uses servlet-api 3.1, and specifying version 3.0.1 was breaking
"mvn gwt:devmode" when Java would fail to find HttpSessionIdListener
needed by Jetty.
Removing the version from the POM makes it use the version from the GWT
"BOM" in dependencyManagement.

Also, servlet-api should have had the 'provided' scope to not be bundled
in the WAR's WEB-INF/lib.

Change-Id: I79e1db9ef7c47109fb9eefd5687a6207c6d12632
diff --git a/samples/dynatablerf/pom.xml b/samples/dynatablerf/pom.xml
index b68d432..ad250d5 100644
--- a/samples/dynatablerf/pom.xml
+++ b/samples/dynatablerf/pom.xml
@@ -57,7 +57,7 @@
     <dependency>
       <groupId>javax.servlet</groupId>
       <artifactId>javax.servlet-api</artifactId>
-      <version>3.0.1</version>
+      <scope>provided</scope>
     </dependency>
 
     <dependency>