chore(pmd): remove deprecated AbstractNaming rule

Quote from https://pmd.github.io/2018/04/29/PMD-6.3.0/#deprecated-rules
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The Java rule AbstractNaming (java-codestyle) is deprecated in favour of ClassNamingConventions.
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See also https://pmd.github.io/2018/04/29/PMD-6.3.0/#naming-rules-enhancements

Part of #1018

Author: php-coder

src/main/config/pmd.xml

@@ -59,7 +59,6 @@
 	<rule ref="category/java/bestpractices.xml/UseCollectionIsEmpty" />
 	<rule ref="category/java/bestpractices.xml/UseVarargs" />
 
-	<rule ref="category/java/codestyle.xml/AbstractNaming" />
 	<!--<rule ref="category/java/codestyle.xml/AtLeastOneConstructor" />-->
 	<rule ref="category/java/codestyle.xml/AvoidDollarSigns" />
 	<rule ref="category/java/codestyle.xml/AvoidFinalLocalVariable" />