Remove outdated info from manual.

doc/manual.html

@@ -441,8 +441,7 @@
     by <code>pre</code> elements. By default no text styling (such as
     bold) that might change line height is applied. If you do want
     such effects, you'll have to give <code>CodeMirror pre</code> a
-    fixed height. Also, you must still take care that character width
-    is constant.</p>
+    fixed height.</p>
 
     <p>If your page's style sheets do funky things to
     all <code>div</code> or <code>pre</code> elements (you probably