[MCLEAN-113] Downgrade plexus-xml to 3.0.0

It is only needed for testing so move to test scope
diff --git a/pom.xml b/pom.xml
index c379f45..a6a714c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -77,12 +77,6 @@
       <artifactId>plexus-utils</artifactId>
       <version>4.0.0</version>
     </dependency>
-    <dependency>
-      <groupId>org.codehaus.plexus</groupId>
-      <artifactId>plexus-xml</artifactId>
-      <version>4.0.0</version>
-      <scope>provided</scope>
-    </dependency>
 
     <!-- dependencies to annotations -->
     <dependency>
@@ -99,6 +93,12 @@
       <scope>test</scope>
     </dependency>
     <dependency>
+      <groupId>org.codehaus.plexus</groupId>
+      <artifactId>plexus-xml</artifactId>
+      <version>3.0.0</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
       <groupId>org.apache.maven</groupId>
       <artifactId>maven-compat</artifactId>
       <version>${mavenVersion}</version>