REFACTOR: Simplify Trans Number handling

Previously there was a check for the presence of "Trans Number".
But if 'use-split-action' the options will always contain
the toggle 'Trans Number'. Therefore remove unnecessary check.

gnucash/report/standard-reports/transaction.scm

@@ -745,9 +745,7 @@ Credit Card, and Income accounts."))))))
              (_ "Reconciled Date"))
      (add-if (column-uses? 'num columns-used)
              (if (and (qof-book-use-split-action-for-num-field (gnc-get-current-book))
-                      (if (gnc:lookup-option options gnc:pagename-display (N_ "Trans Number"))
-                          (opt-val gnc:pagename-display (N_ "Trans Number"))
-                          #f))
+                      (opt-val gnc:pagename-display (N_ "Trans Number")))
                  (_ "Num/T-Num")
                  (_ "Num")))
      (add-if (column-uses? 'description columns-used)