Remove redundant groupId from pom.

The project groupId matches the parent groupId.
diff --git a/commons-statistics-distribution/pom.xml b/commons-statistics-distribution/pom.xml
index bde7cd5..03ba681 100644
--- a/commons-statistics-distribution/pom.xml
+++ b/commons-statistics-distribution/pom.xml
@@ -26,7 +26,6 @@
     <version>1.0-SNAPSHOT</version>
   </parent>
 
-  <groupId>org.apache.commons</groupId>
   <artifactId>commons-statistics-distribution</artifactId>
   <version>1.0-SNAPSHOT</version>
   <name>Apache Commons Statistics Distribution</name>
diff --git a/commons-statistics-regression/pom.xml b/commons-statistics-regression/pom.xml
index 402cbd1..38792b3 100644
--- a/commons-statistics-regression/pom.xml
+++ b/commons-statistics-regression/pom.xml
@@ -26,7 +26,6 @@
     <version>1.0-SNAPSHOT</version>
   </parent>
 
-  <groupId>org.apache.commons</groupId>
   <artifactId>commons-statistics-regression</artifactId>
   <version>1.0-SNAPSHOT</version>
   <name>Apache Commons Statistics Regression</name>
diff --git a/dist-archive/pom.xml b/dist-archive/pom.xml
index 4736e51..8ccab61 100644
--- a/dist-archive/pom.xml
+++ b/dist-archive/pom.xml
@@ -26,7 +26,6 @@
     <version>1.0-SNAPSHOT</version>
   </parent>
 
-  <groupId>org.apache.commons</groupId>
   <artifactId>commons-statistics</artifactId>
   <version>1.0-SNAPSHOT</version>
   <packaging>pom</packaging>