Add PR to the changelog

Author: vy

src/changelog/.2.x.x/add_getConfiguration_method_for_mulitiple_URIs.xml

@@ -7,6 +7,7 @@
   type="added">
   <issue id="3775" link="https://github.com/apache/logging-log4j2/issues/3775"/>
   <issue id="3921" link="https://github.com/apache/logging-log4j2/pull/3921"/>
+  <issue id="3921" link="https://github.com/apache/logging-log4j2/pull/3921"/>
   <description format="asciidoc">
     Add a new `ConfigurationFactory::getConfiguration` method accepting multiple `URI`s
   </description>