♻️ Favor cl- functions

When requiring `rpgdm.el` and it's "child" packages, I encounter the
following warnings:

> Warning: ‘destructuring-bind’ is an obsolete alias (as of 27.1); use
> ‘cl-destructuring-bind’ instead.
>
> Warning: ‘incf’ is an obsolete alias (as of 27.1); use ‘cl-incf’
> instead.
>
> Warning: ‘decf’ is an obsolete alias (as of 27.1); use ‘cl-decf’
> instead.
>
> Warning: ‘defstruct’ is an obsolete alias (as of 27.1); use
> ‘cl-defstruct’ instead.

Since we've already required the `cl` package, this should be a noop change.

rpgdm-tables-dice.el

@@ -17,7 +17,7 @@
 
 ;;; Code:
 
-(defstruct dice-table dice rows)
+(cl-defstruct dice-table dice rows)
 
 (defun rpgdm-tables--choose-dice-table (table)
   "Choose a string from a random dice table."