website: drop the duplicate landing language switch

The landing showed two language switches: the hero #lang-switch button and
the header nav language dropdown (used on every other page). Remove the
redundant hero button and its now-dead CSS; the nav dropdown is the single
switcher, and it already records the choice in localStorage for the root
auto-route.

Author: changkun

website/themes/moderncpp/layout/index.ejs

@@ -12,18 +12,6 @@
   </div>
 </div>
 
-<div id="lang-switch">
-  <% if (isEn) { %>
-    <a class="lang-btn" href="<%- url_for("/modern-cpp/") %>" onclick="try{localStorage.setItem('mcpp-lang','zh')}catch(e){}">
-      <span class="flag" style="content: url(/modern-cpp/assets/lang/cn.svg); display: inline-block; width: 15px; height: 15px; vertical-align: middle; margin-right: 6px; margin-bottom: 2px;"></span>中文
-    </a>
-  <% } else { %>
-    <a class="lang-btn" href="<%- url_for("/modern-cpp/en/") %>" onclick="try{localStorage.setItem('mcpp-lang','en')}catch(e){}">
-      <span class="flag" style="content: url(/modern-cpp/assets/lang/en.svg); display: inline-block; width: 15px; height: 15px; vertical-align: middle; margin-right: 6px; margin-bottom: 2px;"></span>English
-    </a>
-  <% } %>
-</div>
-
 <% if (isEn) { %>
   <div id="hero">
     <div class="inner">

website/themes/moderncpp/source/modern-cpp/css/index.styl

@@ -22,34 +22,6 @@ body
     .logo
       display: none
 
-#lang-switch
-  text-align: center
-  padding: 90px 40px 0 200px
-  a.lang-btn
-    display: inline-block
-    text-decoration: none
-    background: transparent
-    border: 1px solid rgba(126, 45, 54, 0.4)
-    color: $theme
-    font-size: 0.95em
-    font-weight: 600
-    letter-spacing: .05em
-    padding: 6px 16px
-    margin: 0 4px
-    border-radius: 4px
-    cursor: pointer
-    transition: all .2s ease
-    &:hover
-      background: $theme
-      color: #fff
-      border-color: $theme
-    .flag
-      width: 15px
-      height: 15px
-      margin-right: 6px
-      vertical-align: middle
-      margin-bottom: 2px
-
 #hero
   padding: 60px 40px 40px 200px
   background-color: #fff
@@ -115,8 +87,6 @@ body
     display: none
   #mobile-bar
     display: block
-  #lang-switch
-    padding: 70px 40px 0
   #hero
     padding: 20px 40px 50px
     .hero-logo