github-release: do create a discussion post for each new Git for Windows version

This was the intention of 0718129 (release: create a discussion for
every Git for Windows release, 2024-07-02), but it changed the call that
creates the draft release.

Apparently the intention to create a discussion post is _not_ stored
when creating a draft release, though, sadly. Therefore we need to state
that intention again when we do publish the release.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/actions/github-release/action.yml

@@ -147,7 +147,8 @@ runs:
             release.id, {
               draft: false,
               prerelease: isPrerelease,
-              make_latest : !isPrerelease
+              make_latest : !isPrerelease,
+              discussion_category_name: 'Announcements',
             }
           )
     - name: update check-run