Make addTags() non-virtual

src/pv/ntattribute.h

@@ -45,7 +45,7 @@ namespace detail {
          * Adds tags field to the NTAttribute.
          * @return this instance of <b>NTAttributeBuilder</b>.
          */
-        virtual shared_pointer addTags();
+        shared_pointer addTags();
 
         /**
          * Adds descriptor field to the NTAttribute.

src/pv/ntndarrayAttribute.h

@@ -45,7 +45,7 @@ namespace detail {
          * Adds tags field to the NTNDArrayAttribute.
          * @return this instance of <b>NTNDArrayAttributeBuilder</b>.
          */
-        virtual shared_pointer addTags();
+        shared_pointer addTags();
 
         /**
          * Adds descriptor field to the NTNDArrayAttribute.