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

llvm-svn: 155153
diff --git a/llvm/docs/HowToReleaseLLVM.html b/llvm/docs/HowToReleaseLLVM.html
index 396b4fe..382e18f 100644
--- a/llvm/docs/HowToReleaseLLVM.html
+++ b/llvm/docs/HowToReleaseLLVM.html
@@ -4,7 +4,7 @@
 <head>
   <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
   <title>How To Release LLVM To The Public</title>
-  <link rel="stylesheet" href="llvm.css" type="text/css">
+  <link rel="stylesheet" href="_static/llvm.css" type="text/css">
 </head>
 <body>