Revert "org-agenda.el: Fix handling of one-time delays"

* lisp/org-agenda.el (org-agenda-get-scheduled): Revert changes from
39c656870, which introduced a regression that prevents repeating tasks
from appearing for future dates.

The regression, reported in late February, seems likely to affect more
users than the one-time delay handling fixed by 39c656870
(org-agenda.el: Fix handling of one-time delays, 2020-02-01).  As we
don't have a proposed fix at the moment, let's revert 39c656870.

Reported-by: Gustavo Barros <gusbrs.2016@gmail.com>
  <87imjqdtpo.fsf@gmail.com>

lisp/org-agenda.el

@@ -6298,10 +6298,6 @@ scheduled items with an hour specification like [h]h:mm."
 			    (org-agenda--timestamp-to-absolute deadline))
 			 org-scheduled-delay-days))
 		   (t 0))))
-	       (diff-r (abs (- repeat current)))
-	       (ddays-once (or (and (string-match "--\\([0-9]+\\)[hdwmy]" s)
-				    (string-to-number (match-string 1 s)))
-			       0))
 	       (ddays
 		(cond
 		 ;; Nullify delay when a repeater triggered already
@@ -6320,25 +6316,13 @@ scheduled items with an hour specification like [h]h:mm."
 	  (unless (and todayp
 		       habitp
 		       (bound-and-true-p org-habit-show-all-today))
-	    (when (or
-		   ;; no one-time delay, not repeated delay
-		   (and (not ddays-once) (not (= ddays diff-r)))
-		   ;; one-time delay, but not for today
-		   (and ddays-once
-			(not (= diff diff-r))
-			(= ddays-once diff-r))
-		   ;; normal delay, but already in the past
-		   (and (> ddays 0) (< diff ddays))
-		   ;; a habit, but past `org-habit-scheduled-past-days'
-		   (> diff (or (and habitp org-habit-scheduled-past-days)
-			       org-scheduled-past-days))
-		   ;; schedule in the future
-		   (> schedule current)
-		   ;; no delay, not scheduled today, no deadline for today
-		   (and (= ddays 0)
-			(/= current schedule)
-			(/= current today)
-			(/= current repeat)))
+	    (when (or (and (> ddays 0) (< diff ddays))
+		      (> diff (or (and habitp org-habit-scheduled-past-days)
+				  org-scheduled-past-days))
+		      (> schedule current)
+		      (and (/= current schedule)
+			   (/= current today)
+			   (/= current repeat)))
 	      (throw :skip nil)))
 	  ;; Possibly skip done tasks.
 	  (when (and donep