Use HTTPS to fetch XSD file

Author: garydgregory

src/changes/changes.xml

@@ -18,7 +18,7 @@
 <!-- Description: http://maven.apache.org/plugins/maven-changes-plugin/changes.html -->
 <document xmlns="http://maven.apache.org/changes/2.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xsi:schemaLocation="http://maven.apache.org/changes/2.0.0 http://maven.apache.org/xsd/changes-2.0.0.xsd">
+          xsi:schemaLocation="http://maven.apache.org/changes/2.0.0 https://maven.apache.org/xsd/changes-2.0.0.xsd">
   <properties>
     <title>Apache Commons Release Plugin Changes</title>
     <author email="[email protected]">Apache Commons Developers</author>