Merge pull request #13 from apache/dependabot/maven/freemarker-docgen-core/xalan-xalan-2.7.3

Bump xalan:xalan from 2.7.2 to 2.7.3 in /freemarker-docgen-core

As mentionned at https://xalan.apache.org/
<<The current release among other Xalan-J implementation features, fixes a Xalan-J XSLTC security issue that was registered against version 2.7.2.>>
diff --git a/freemarker-docgen-core/pom.xml b/freemarker-docgen-core/pom.xml
index e804d85..a53090d 100644
--- a/freemarker-docgen-core/pom.xml
+++ b/freemarker-docgen-core/pom.xml
@@ -95,7 +95,7 @@
             <!-- Needed on Java 9+ -->
             <groupId>xalan</groupId>
             <artifactId>xalan</artifactId>
-            <version>2.7.2</version>
+            <version>2.7.3</version>
             <exclusions>
                 <exclusion>
                     <groupId>xml-apis</groupId>