Fix navbar + menu flashing on page load (#31281)

Fixes
https://github.com/go-gitea/gitea/pull/31273#issuecomment-2153771331.
Same method as used in https://github.com/go-gitea/gitea/pull/30215. All
left-opening dropdowns need to use it method.

---------

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

templates/base/head_navbar.tmpl

@@ -4,7 +4,7 @@
 {{end}}
 
 <nav id="navbar" aria-label="{{ctx.Locale.Tr "aria.navbar"}}">
-	<div class="navbar-left ui secondary menu">
+	<div class="navbar-left">
 		<!-- the logo -->
 		<a class="item" id="navbar-logo" href="{{AppSubUrl}}/" aria-label="{{if .IsSigned}}{{ctx.Locale.Tr "dashboard"}}{{else}}{{ctx.Locale.Tr "home"}}{{end}}">
 			<img width="30" height="30" src="{{AssetUrlPrefix}}/img/logo.svg" alt="{{ctx.Locale.Tr "logo"}}" aria-hidden="true">
@@ -61,7 +61,7 @@
 	</div>
 
 	<!-- the full dropdown menus -->
-	<div class="navbar-right ui secondary menu">
+	<div class="navbar-right">
 		{{if and .IsSigned .MustChangePassword}}
 			<div class="ui dropdown jump item" data-tooltip-content="{{ctx.Locale.Tr "user_profile_and_more"}}">
 				<span class="text tw-flex tw-items-center">
@@ -104,7 +104,7 @@
 					<span class="not-mobile">{{svg "octicon-triangle-down"}}</span>
 					<span class="only-mobile">{{ctx.Locale.Tr "create_new"}}</span>
 				</span>
-				<div class="menu left">
+				<div class="menu">
 					<a class="item" href="{{AppSubUrl}}/repo/create">
 						{{svg "octicon-plus"}} {{ctx.Locale.Tr "new_repo"}}
 					</a>