STYLE: consistent use of '= delete' for removed constructors/assignments

- make the purpose more explicit, and reduces some work for the
  compiler as well.

src/functionObjects/field/fieldAverage/fieldAverage.H

@@ -274,10 +274,10 @@ protected:
             void readAveragingProperties();
 
 
-        //- Disallow default bitwise copy construct
+        //- No copy construct
         fieldAverage(const fieldAverage&) = delete;
 
-        //- Disallow default bitwise assignment
+        //- No copy assignment
         void operator=(const fieldAverage&) = delete;