[pom] Update maven-pmd-plugin to 3.8
[pom] Update maven-pmd-plugin to 3.8

hazendaz/waffle,dblock/waffle,dblock/waffle,Waffle/waffle,Waffle/waffle,hazendaz/waffle,hazendaz/waffle,dblock/waffle,dblock/waffle,Waffle/waffle