Backport commit 0c6c8aa00 from Emacs

See discussion at
https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00749.html .

* lisp/org-element.el (org-element--cache-sync-requests):
* lisp/org.el (org-sparse-tree):
Remove redundant backslashes.

Remove (or double) redundant backslashes in string literals
0c6c8aa002d321db61afdd14c70744f7bc27f268
Mattias Engdegård
Fri Jan 24 23:04:34 2020 +0100

lisp/org-element.el

@@ -4891,7 +4891,7 @@ with `org-element--cache-compare'.  This cache is used in
 
 A request is a vector with the following pattern:
 
- \[NEXT BEG END OFFSET PARENT PHASE]
+ [NEXT BEG END OFFSET PARENT PHASE]
 
 Processing a synchronization request consists of three phases:
 

lisp/org.el

@@ -10732,8 +10732,8 @@ D      Show deadlines and scheduled items between a date range."
   (setq type (or type org-sparse-tree-default-date-type))
   (setq org-ts-type type)
   (message "Sparse tree: [r]egexp [t]odo [T]odo-kwd [m]atch [p]roperty
-             \[d]eadlines [b]efore-date [a]fter-date [D]ates range
-             \[c]ycle through date types: %s"
+             [d]eadlines [b]efore-date [a]fter-date [D]ates range
+             [c]ycle through date types: %s"
 	   (cl-case type
 	     (all "all timestamps")
 	     (scheduled "only scheduled")