Revert 533aea11fd

The extra padding causes the first line of each markdown rendered code block to be indented, but does not indent the rest of the code block, resulting in a jagged left edge. Removing this bit of CSS restores a flat left edge.

You can verify this by trying to render the following:

    abc
        def
        ghi

notebook/static/notebook/less/renderedhtml.less

@@ -52,7 +52,6 @@
 
     code {
         background-color: #eff0f1;
-        padding: 1px 5px;
     }
 
     pre code {background-color: @body-bg;}