[docs] Update HTML pages to refer to CSS in a way that works locally and with Sphinx.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155153 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index e5f3047..be67b6d 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -3,7 +3,7 @@
 <html>
 <head>
   <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
-  <link rel="stylesheet" href="llvm.css" type="text/css">
+  <link rel="stylesheet" href="_static/llvm.css" type="text/css">
   <title>LLVM 3.1 Release Notes</title>
 </head>
 <body>