fix(css): fix some css bugs

assets/css/_partial/_post/_code.scss

@@ -34,9 +34,8 @@ p > code {
 // chroma
 .highlight > .chroma {
   margin: 1em 0;
-  border-radius: 5px;
+  border-radius: 6px;
   overflow-x: auto;
-  box-shadow: 1px 1px 2px rgba(0,0,0,0.125);
   position: relative;
   background: $code-background-color;
 
@@ -66,7 +65,7 @@ p > code {
   }
 
   @each $sign, $text in $code-type-list {
-    &.#{$sign} table::after {
+    & .#{$sign} table::after {
       content: $text;
     }
   }
@@ -119,7 +118,7 @@ p > code {
   }
 }
 
-.code {
+.highlight {
   /* Parentheses */ .p { color: #A9A9B3 }
   /* Keyword */  .k { color: #859900 }
   /* KeywordConstant */  .kc { color: #859900; font-weight: bold }