Remove the unsupported "mysql 6.x" from sonar.properties

sonar-application/src/main/assembly/conf/sonar.properties

@@ -55,7 +55,7 @@ sonar.jdbc.url:                            jdbc:h2:tcp://localhost:9092/sonar
 #sonar.embeddedDatabase.port:               9092
 
 
-#----- MySQL 5.x/6.x
+#----- MySQL 5.x
 # Comment the embedded database and uncomment the following line to use MySQL
 #sonar.jdbc.url:                            jdbc:mysql://localhost:3306/sonar?useUnicode=true&characterEncoding=utf8&rewriteBatchedStatements=true