improve ledger-reconcile-toggle key binding

Actually, revert @jgertm's change that I asked to make. As @bmag explained, this
is very useful key binding that is similar to C-c C-c as it allows to quickly
access functionality by pressing `dotspacemacs-major-mode-leader-key` twice.
Also note that `dotspacemacs-major-mode-leader-key` can be nil, that's why we
have to handle this value as well.

layers/+tools/finance/packages.el

@@ -44,7 +44,7 @@
          "y" 'ledger-set-year
          "RET" 'ledger-set-month)
       (spacemacs/set-leader-keys-for-major-mode 'ledger-reconcile-mode
-        "," 'ledger-reconcile-toggle
+        (or dotspacemacs-major-mode-leader-key ",") 'ledger-reconcile-toggle
         "a" 'ledger-reconcile-add
         "q" 'ledger-reconcile-quit
         "t" 'ledger-reconcile-change-target