Below is the reported error when I run TestNG.xml. Even though I changed the scope to compile, it still is not fixed. I've also built the project again. I would appreciate if someone can give a feasible solution for this.
Exception in thread "main" org.testng.TestNGException:
6.1.1 is not a supported TestNG version
  at org.testng.remote.support.ServiceLoaderHelper.getFirst(ServiceLoaderHelper.java:22)
  at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:43)
Project's pom.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>TestVagrant</groupId>
    <artifactId>1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.seleniumhq.selenium</groupId>
            <artifactId>selenium-java</artifactId>
            <version>2.46.0</version>
        </dependency>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>6.1.1</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>io.appium</groupId>
            <artifactId>java-client</artifactId>
            <version>3.0.0</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>
Below is the TestNG XML:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="Suite">
  <test name="Test">
    <classes>
      <class name="scenarios.AppiumTest"/>
    </classes>
  </test> <!-- Test -->
</suite> <!-- Suite -->
 
    