[FLINK-4732] remove maven junction plugin

On Windows, the plugin downloads and executes code from the author's
web site. The downloaded file is not signed in the same way as Maven
artifacts from Maven central which have to be signed with the
developer's key. This could be a potential target for attackers.

This closes apache#2586

flink-dist/pom.xml

@@ -268,35 +268,6 @@ under the License.
 				</configuration>
 			</plugin>
 
-			<!-- create a symbolic link to the build target in the root directory -->
-			<plugin>
-				<groupId>com.pyx4j</groupId>
-				<artifactId>maven-junction-plugin</artifactId>
-				<version>1.0.3</version>
-				<executions>
-					<execution>
-						<phase>package</phase>
-						<goals>
-							<goal>link</goal>
-						</goals>
-					</execution>
-					<execution>
-						<id>unlink</id>
-						<phase>pre-clean</phase>
-						<goals>
-							<goal>unlink</goal>
-						</goals>
-					</execution>
-				</executions>
-				<configuration>
-					<links>
-						<link>
-							<dst>${project.basedir}/../build-target</dst>
-							<src>${project.basedir}/target/flink-${project.version}-bin/flink-${project.version}</src>
-						</link>
-					</links>
-				</configuration>
-			</plugin>
 		</plugins>
 	</build>
 </project>