ReFix font-weight of <strong> element for CJK fonts (#5920)

Also apply to Japanese and Korean.
Fix font-weight in landing pages.

app/javascript/styles/mastodon/about.scss

@@ -19,7 +19,7 @@
     display: inline;
     margin: 0;
     padding: 0;
-    font-weight: 500;
+    font-weight: 700;
     background: transparent;
     font-family: inherit;
     font-size: inherit;
@@ -381,12 +381,6 @@
         font-weight: 500;
         font-size: 32px;
         line-height: 48px;
-
-        @each $lang in $cjk-langs {
-          &:lang(#{$lang}) {
-            font-weight: 700;
-          }
-        }
       }
     }
 

app/javascript/styles/mastodon/variables.scss

@@ -29,4 +29,4 @@ $ui-secondary-color: $classic-secondary-color !default;        // Lightest
 $ui-highlight-color: $classic-highlight-color !default;        // Vibrant
 
 // Language codes that uses CJK fonts
-$cjk-langs: zh-CN, zh-HK, zh-TW;
+$cjk-langs: ja, ko, zh-CN, zh-HK, zh-TW;