Fix typo in build-ref.html

Closes #13467.

PiperOrigin-RevId: 373181725

site/docs/build-ref.html

@@ -183,7 +183,7 @@ <h3 id="labels">Labels</h3>
   The second part of the label is the un-qualified package name
   <code>my/app/main</code>, the path to the package
   relative to the repository root.  Together, the repository name and the
-  un-qualfied package name form the fully-qualified package name
+  un-qualified package name form the fully-qualified package name
   <code>@myrepo//my/app/main</code>. When the label refers to the same
   package it is used in, the package name (and optionally, the colon)
   may be omitted.  So, inside <code>@myrepo//my/app/main</code>,