Update section heading.
RELNOTES: None.
@@ -169,7 +169,7 @@ nav: docs
<li><a href="/versions/{{ site.version }}/toolchains.html">Toolchains</a></li>
</ul>
- <h3>Extend Bazel</h3>
+ <h3>Extending Bazel</h3>
<ul class="sidebar-nav">
<li><a href="/versions/{{ site.version }}/skylark/concepts.html">Overview</a></li>
