Remove some padding from code blocks

This creates a weird "leading indent" on the first line of code blocks, at least in Chrome 46, and ends up making the first row not line up nicely with everything else.

app/assets/stylesheets/framework/typography.scss

@@ -17,7 +17,6 @@
     font-family: $monospace_font;
     white-space: pre;
     word-wrap: normal;
-    padding: 1px 2px;
   }
 
   kbd {
@@ -268,4 +267,4 @@ textarea.js-gfm-input {
 
 .strikethrough {
   text-decoration: line-through;
-}
+}
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