Documentation: Update Markdown Site title section

Corrected "is display on the site" to "is displayed on the site" and
other minor rewording.

Change-Id: I6dd3aa67f9e8526e3041ae47816c55a9cecf1426

Documentation/markdown.md

diff --git a/Documentation/markdown.md b/Documentation/markdown.md
index 23020ff..bed3fe7 100644
--- a/Documentation/markdown.md
+++ b/Documentation/markdown.md
@@ -679,9 +679,9 @@
 
 ### Site title
 
-A site wide banner is displayed on all Markdown pages if `navbar.md`
-includes a H1 header.  The text of the header is display on the left
-side of the banner.
+A site-wide banner is displayed on all Markdown pages if `navbar.md`
+includes an H1 header.  The text of the header is displayed on the
+left side of the banner.
 
 ```
 # Gitiles