Add missing anchor.
The "initial conditions" sections is referenced in the "test sharding" section,
so it needs an anchor.
@@ -190,7 +190,7 @@ success or failure based on the exit code observed from the main process. The
test runner may kill any stray processes. Tests should not leak processes in
this fashion.</p>
-<h2>Initial conditions</h2>
+<h2 id="initial-conditions">Initial conditions</h2>
<p>When executing a test, the test runner must establish certain initial
conditions.</p>
