Downgrade impsort to support JDK 11

Author: gnodet

pom.xml

@@ -1008,7 +1008,7 @@
                 <plugin>
                     <groupId>net.revelc.code</groupId>
                     <artifactId>impsort-maven-plugin</artifactId>
-                    <version>1.11.0</version>
+                    <version>1.9.0</version>
                     <configuration>
                         <lineEnding>LF</lineEnding>
                         <groups>java.,javax.,org.w3c.,org.xml.,junit.</groups>