forge--github-repository-query: Fix unpagination of discussions

The field used for singular queries has to be used as the first
field, because only that is placed in the lineage.

(While it would theoretically be possible to remove this requirement,
doing so would require a lot of awkward code (which I did not succeed
in writing in a late-night session), and it would not be worth the
effort.)

Re #843.

Author: tarsius

lisp/forge-github.el

@@ -98,9 +98,9 @@
        (  discussions [(:edges t)
                        (:singular discussion number)
                        (orderBy ((field UPDATED_AT) (direction DESC)))]
+          number
           id
           databaseId
-          number
           url
           stateReason
           ;; Discussions lack isReadByViewer.