Renamed and updated changelog. (apache#3086)

Author: JWT007

src/changelog/.3.x.x/3086_change_RegexFilter_remove_patternflags_from_PluginFactory.xml src/changelog/.3.x.x/3086_change_RegexFilter_cleanup_API.xml

@@ -5,6 +5,6 @@
        type="fixed">
   <issue id="3086" link="https://github.com/apache/logging-log4j2/issues/3086"/>
   <description format="asciidoc">
-    Removed 'patternFlags' @PluginAttribute from RegexFilter @PluginFactory createFilter.
+    Reworked API for RegexFilter: added getXXX for configuration attributes, removed deprecated API.
   </description>
 </entry>