Drop unused commons-lang 2.6 from management (#661)

diff --git a/pom.xml b/pom.xml
index 9004b0a..fcb50d9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -203,11 +203,6 @@
         </exclusions>
       </dependency>
       <dependency>
-        <groupId>commons-lang</groupId>
-        <artifactId>commons-lang</artifactId>
-        <version>2.6</version>
-      </dependency>
-      <dependency>
         <groupId>org.apache.maven.plugin-testing</groupId>
         <artifactId>maven-plugin-testing-harness</artifactId>
         <version>3.3.0</version>