wipe out dead code, fix build

Signed-off-by: Alex Meijer <ameijer@kubecost.com>
(cherry picked from commit f834c385bc8ee37b5bee339daedc0ca540de7ece)

pkg/costmodel/csv_export.go

@@ -309,7 +309,6 @@ func (e *csvExporter) writeCSVToWriter(ctx context.Context, w io.Writer, dates [
 			},
 		})
 	}
-	csvDef = append(csvDef)
 
 	header := make([]string, 0, len(csvDef))
 	for _, def := range csvDef {