org-agenda: Fix docstrings

* lisp/org-agenda.el (org-agenda-skip-scheduled-if-done): Tiny rewording.
(org-agenda-skip-deadline-if-done): Fix typo.

lisp/org-agenda.el

@@ -844,10 +844,9 @@ restricted to unfinished TODO entries only."
 
 (defcustom org-agenda-skip-scheduled-if-done nil
   "Non-nil means don't show scheduled items in agenda when they are done.
-This is relevant for the daily/weekly agenda, not for the TODO list.  And
-it applies only to the actual date of the scheduling.  Warnings about
-an item with a past scheduling dates are always turned off when the item
-is DONE."
+This is relevant for the daily/weekly agenda, not for the TODO list.  It
+applies only to the actual date of the scheduling.  Warnings about an item
+with a past scheduling dates are always turned off when the item is DONE."
   :group 'org-agenda-skip
   :group 'org-agenda-daily/weekly
   :type 'boolean)
@@ -896,8 +895,8 @@ several times."
 (defcustom org-agenda-skip-deadline-if-done nil
   "Non-nil means don't show deadlines when the corresponding item is done.
 When nil, the deadline is still shown and should give you a happy feeling.
-This is relevant for the daily/weekly agenda.  And it applied only to the
-actually date of the deadline.  Warnings about approaching and past-due
+This is relevant for the daily/weekly agenda.  It applies only to the
+actual date of the deadline.  Warnings about approaching and past-due
 deadlines are always turned off when the item is DONE."
   :group 'org-agenda-skip
   :group 'org-agenda-daily/weekly