add yarn.version for profile yarn and yarn-alpha

Now use "mvn -Pyarn -DskipTests clean package" to build will get error because of the yarn.version default value 0.23.7. So add the yarn.version for profile yarn and yarn-alpha, then "mvn -Pyarn -DskipTests clean package" and "mvn -Pyarn-alpha -DskipTests clean package" build both success.