Clean up `gridfunctionspaceutilities.hh`

This is an issue from the March 2017 PDELab Meeting.

@joe do you remember, what type of cleanup was intended here?

No, no idea (without actually looking at the file).

From the meeting minutes it looks to me like this was a point brought up by Steffen?

@smuething Gonna close this, please reopen with more info if you disagree.

closed