[#969] Reorganized code a little bit to facilitate (hopefully) comple…

…tion support for nested sub-subcommands

picocli-shell-jline3/src/main/java/picocli/shell/jline3/PicocliCommands.java

@@ -85,7 +85,7 @@ private SystemCompleter compileCompleters(SystemCompleter completer, CommandLine
 
             // TODO support nested sub-subcommands (https://github.com/remkop/picocli/issues/969)
             //   Is the below sufficient?
-            //   compileCompleters(out, sub.commandLine());
+            //   compileCompleters(completer, sub.commandLine());
         }
         return completer;
     }