Avoid treating a number as an enum in manual

* doc/org-manual.org (The Agenda Dispatcher): Avoid treating
number as enum.  The previous formatting contained "1." list at
the beginning of line.

doc/org-manual.org

@@ -8557,8 +8557,8 @@ commands:
   Search for a regular expression in all agenda files and additionally
   in the files listed in ~org-agenda-text-search-extra-files~.  This
   uses the Emacs command ~multi-occur~.  A prefix argument can be used
-  to specify the number of context lines for each match, default is
-  1.
+  to specify the number of context lines for each match, the default
+  is 1.
 
 - {{{kbd(#)}}} ::