fix(github): set discussion category on publish only

It has no effect if the release is a draft, and seems to be ignored
later when published.

Move setting the discussion category to the publish method only.

Closes https://github.com/orgs/goreleaser/discussions/4902

internal/client/github.go

@@ -390,10 +390,6 @@ func (c *githubClient) CreateRelease(ctx *context.Context, body string) (string,
 		MakeLatest: github.String("true"),
 	}
 
-	if ctx.Config.Release.DiscussionCategoryName != "" {
-		data.DiscussionCategoryName = github.String(ctx.Config.Release.DiscussionCategoryName)
-	}
-
 	if target := ctx.Config.Release.TargetCommitish; target != "" {
 		target, err := tmpl.New(ctx).Apply(target)
 		if err != nil {
@@ -425,9 +421,13 @@ func (c *githubClient) PublishRelease(ctx *context.Context, releaseID string) er
 	if err != nil {
 		return fmt.Errorf("non-numeric release ID %q: %w", releaseID, err)
 	}
-	if _, err := c.updateRelease(ctx, releaseIDInt, &github.RepositoryRelease{
+	data := &github.RepositoryRelease{
 		Draft: github.Bool(draft),
-	}); err != nil {
+	}
+	if ctx.Config.Release.DiscussionCategoryName != "" {
+		data.DiscussionCategoryName = github.String(ctx.Config.Release.DiscussionCategoryName)
+	}
+	if _, err := c.updateRelease(ctx, releaseIDInt, data); err != nil {
 		return fmt.Errorf("could not update existing release: %w", err)
 	}
 	return nil