fix help page mentioning outdated rustdoc benchmarks syntax

site/static/help.html

@@ -40,14 +40,11 @@ <h3><b><code>@rust-timer</code> commands</b></h3>
         </p>
         <p><code>@rust-timer queue</code> has a few extra options that can be useful:</p>
         <ul>
-            <li><code>include=&lt;INCLUDE&gt;</code> only runs benchmarks with <code>&lt;INCLUDE&gt;</code> in their
-                title. For example, if you just want to run rustdoc benchmarks, do
-                <code>@bors try @rust-timer queue include=-doc</code>; the <code>-doc</code> matches the
-                <code>-doc</code> appended to rustdoc benchmarks. <code>&lt;INCLUDE&gt;</code> is a comma-separated list
-                of substrings; only one of the items in the list of substrings must match.
+            <li><code>include=&lt;INCLUDE&gt;</code> is a comma-separated list of benchmark prefixes. A benchmark is included in
+                the run only if its name matches one of the given prefixes.
             </li>
-            <li><code>exclude=&lt;EXCLUDE&gt;</code> is similar to <code>include=</code>, but instead skips any
-                benchmarks that have one of the items in the list of substrings as a substring of its name.</li>
+            <li><code>exclude=&lt;EXCLUDE&gt;</code> is a comma-separated list of benchmark prefixes, and the inverse of <code>include=</code>.
+                A benchmark is excluded from the run if its name matches one of the given prefixes.</li>
             <li><code>runs=&lt;RUNS&gt;</code> configures how many times the benchmark is run. <code>&lt;RUNS&gt;</code>
                 is an integer. All benchmarks run at least once by default, but some run more than one time. You can use
                 the <code>runs</code> option to override the default run count and make every benchmark run for