Fix error reporting for abstract naming sniff (#50)

Previously the error message showed a placeholder rather than the class
name, like this:

    Abstract class name "%s" must be prefixed with "Abstract"

It now shows the class name, like this:

    Abstract class name "Foo" must be prefixed with "Abstract"

PHP/CodeSniffer/Graze/Sniffs/Naming/AbstractClassNamingSniff.php

@@ -75,7 +75,7 @@ public function process(File $phpcsFile, $stackPtr)
             $className = $phpcsFile->getDeclarationName($stackPtr);
 
             if (substr($className, 0, 8) !== 'Abstract') {
-                $phpcsFile->addError('Abstract class name "%s" must be prefixed with "Abstract"', $stackPtr, static::ERROR_CODE, '', [$className]);
+                $phpcsFile->addError('Abstract class name "%s" must be prefixed with "Abstract"', $stackPtr, static::ERROR_CODE, [$className]);
             }
         }
     }