Ui correction in mobile view nav bar left aligned items. (#27046)

As title
From the long time I was looking for this UI, Now its the time to fix
it.

Before
<img width="252" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/963f2cb4-5cfd-4a14-ab85-88e25c3daef5">

<img width="502" alt="image"
src="https://github.com/go-gitea/gitea/assets/80308335/58453ef1-2555-4568-95d0-5293055b33b8">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

web_src/css/modules/navbar.css

@@ -31,7 +31,6 @@
   padding-top: 3px;
   padding-bottom: 3px;
   display: flex;
-  justify-content: center;
 }
 
 #navbar > .menu > .item {