STYLE: argList::opt method instead of the longer argList::lookupOrDefault

- also replaced a few instances of readIfPresent with opt<> for
  constant values.

applications/utilities/mesh/advanced/combinePatchFaces/combinePatchFaces.C

@@ -380,8 +380,7 @@ int main(int argc, char *argv[])
 
     // Sin of angle between two consecutive edges on a face.
     // If sin(angle) larger than this the face will be considered concave.
-    const scalar concaveAngle =
-        args.lookupOrDefault<scalar>("concaveAngle", 30);
+    const scalar concaveAngle = args.opt<scalar>("concaveAngle", 30);
 
     const scalar concaveSin = Foam::sin(degToRad(concaveAngle));