Remove StringUtils#join in favor of String#join (Java 8)

src/main/java/fr/xephi/authme/command/CommandUtils.java

@@ -1,7 +1,6 @@
 package fr.xephi.authme.command;
 
 import com.google.common.collect.Lists;
-import fr.xephi.authme.util.StringUtils;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -25,18 +24,6 @@ public final class CommandUtils {
         return command.getArguments().size();
     }
 
-    /**
-     * Provide a textual representation of a list of labels to show it as a command. For example, a list containing
-     * the items ["authme", "register", "player"] will return "authme register player".
-     *
-     * @param labels The labels to format
-     *
-     * @return The space-separated labels
-     */
-    public static String labelsToString(Iterable<String> labels) {
-        return StringUtils.join(" ", labels);
-    }
-
     public static String constructCommandPath(CommandDescription command) {
         StringBuilder sb = new StringBuilder();
         String prefix = "/";