minor fix solr-jetty-context.xml defaultsDescriptor

I accidentally committed a commenting out of the defaultsDescriptor while merging something totally unrelated.
This probably had no practical effect, as webdefault.xml is itself just the defaults.

Author: dsmiley

solr/server/contexts/solr-jetty-context.xml

@@ -3,7 +3,7 @@
 <Configure class="org.eclipse.jetty.ee10.webapp.WebAppContext">
   <Set name="contextPath"><Property name="hostContext" default="/solr"/></Set>
   <Set name="war"><Property name="jetty.base"/>/solr-webapp/webapp</Set>
-<!--  <Set name="defaultsDescriptor"><Property name="jetty.base"/>/etc/webdefault.xml</Set>-->
+  <Set name="defaultsDescriptor"><Property name="jetty.base"/>/etc/webdefault.xml</Set>
   <Set name="extractWAR">false</Set>
 
   <!--