fix a typo.
Closes
@@ -74,7 +74,7 @@ title: Concepts and Terminology
Encyclopedia and the documentation on
<a href="repo/index.html">embeded Starlark repository rules</a>.</p>
-<p>As external repositories are repositories themselves, they ofen contain
+<p>As external repositories are repositories themselves, they often contain
a <code>WORKSPACE</code> file as well. However, these additional
<code>WORKSPACE</code> files are ignored by Bazel. In particular,
repositories depended upon transitively are not added automatically.</p>
