docs: prefer lowercase html tags

Signed-off-by: Brian Paul <brianp@vmware.com>
diff --git a/docs/postprocess.html b/docs/postprocess.html
index b99ef2b..06a4593 100644
--- a/docs/postprocess.html
+++ b/docs/postprocess.html
@@ -26,7 +26,7 @@
 </p>
 
 
-<H2>PP environment variables</H2>
+<h2>PP environment variables</h2>
 
 <ul>
 <li>PP_DEBUG - If defined debug information will be printed to stderr.