Fix the route for pull-request's authors (#26016) (#26018)

Backport #26016 by @wxiaoguang

Close #25906



![image](https://github.com/go-gitea/gitea/assets/2114189/e689f3e1-9a90-46c0-89f4-2d61394d34d3)


Succeeded logs:

```
[I] router: completed GET /root/test/issues/posters?&q=%20&_=1689853025011 for [::1]:59271, 200 OK in 127.7ms @ repo/issue.go:3505(repo.IssuePosters)


[I] router: completed GET /root/test/pulls/posters?&q=%20&_=1689853968204 for [::1]:59269, 200 OK in 94.3ms @ repo/issue.go:3509(repo.PullPosters)
```

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/issue.go

@@ -3476,8 +3476,15 @@ type userSearchResponse struct {
 
 // IssuePosters get posters for current repo's issues/pull requests
 func IssuePosters(ctx *context.Context) {
+	issuePosters(ctx, false)
+}
+
+func PullPosters(ctx *context.Context) {
+	issuePosters(ctx, true)
+}
+
+func issuePosters(ctx *context.Context, isPullList bool) {
 	repo := ctx.Repo.Repository
-	isPullList := ctx.Params(":type") == "pulls"
 	search := strings.TrimSpace(ctx.FormString("q"))
 	posters, err := repo_model.GetIssuePostersWithSearch(ctx, repo, isPullList, search, setting.UI.DefaultShowFullName)
 	if err != nil {