Use em for code font size instead of rem

This fixes some cases where a user style sheet may be setting a weird base font-size.

extensions/markdown-language-features/media/markdown.css

@@ -135,7 +135,6 @@ h3 code,
 h4 code,
 h5 code,
 h6 code {
-	font-size: inherit;
 	line-height: auto;
 }
 
@@ -168,8 +167,8 @@ blockquote {
 
 code {
 	font-family: Menlo, Monaco, Consolas, "Droid Sans Mono", "Courier New", monospace, "Droid Sans Fallback";
-	font-size: 1rem;
-	line-height: 1.357rem;
+	font-size: 1em;
+	line-height: 1.357em;
 }
 
 body.wordWrap pre {