Completed update ...ErrorIn -> ...ErrorInFunction

Avoids the clutter and maintenance effort associated with providing the
function signature string.

etc/codeTemplates/source/_Template.C

@@ -87,7 +87,7 @@ void Foam::CLASSNAME::operator=(const CLASSNAME& rhs)
     // Check for assignment to self
     if (this == &rhs)
     {
-        FatalErrorIn("Foam::CLASSNAME::operator=(const Foam::CLASSNAME&)")
+        FatalErrorInFunction
             << "Attempted assignment to self"
             << abort(FatalError);
     }