Remove historical reference to test runners from user manual.
MOS_MIGRATED_REVID=148397211
@@ -2699,7 +2699,7 @@ value, merely warns if Bazel thinks the timeout could be restricted further.
<h4 id='flag--test_arg'><code class='flag'>--test_arg <var>arg</var></code></h4>
<p>
- Passes command-line options/flags/arguments to the test (not to the test runner). This
+ Passes command-line options/flags/arguments to each test process. This
option can be used multiple times to pass several arguments, e.g.
<code class='flag'>--test_arg=--logtostderr --test_arg=--v=3</code>.
</p>
