[release] Updated compatibility previous version to the one just released.

Author: michitux

pom.xml

@@ -50,7 +50,7 @@
 
     <!-- The previous stable version of this project to check against for finding backward incompatibility
          (binary and source). -->
-    <xwiki.compatibility.previous.version>18.2.0</xwiki.compatibility.previous.version>
+    <xwiki.compatibility.previous.version>18.2.1</xwiki.compatibility.previous.version>
 
     <!-- Java -->
     <!-- Should be kept in sync with https://dev.xwiki.org/xwiki/bin/view/Community/SupportStrategy/JavaSupportStrategy/ -->