MINOR: update Kafka Streams state.dir doc (#14155)

Default state directory was changes in 2.8.0 release (cf KAFKA-10604)

Reviewers: Guozhang Wang <wangguoz@gmail.com>
diff --git a/docs/streams/developer-guide/config-streams.html b/docs/streams/developer-guide/config-streams.html
index dd9298d..8499099 100644
--- a/docs/streams/developer-guide/config-streams.html
+++ b/docs/streams/developer-guide/config-streams.html
@@ -407,7 +407,7 @@
           <tr class="row-odd"><td>state.dir</td>
             <td>High</td>
             <td colspan="2">Directory location for state stores.</td>
-            <td><code class="docutils literal"><span class="pre">/tmp/kafka-streams</span></code></td>
+            <td><code class="docutils literal"><span class="pre">/${java.io.tmpdir}/kafka-streams</span></code></td>
           </tr>
           <tr class="row-odd"><td>task.timeout.ms</td>
             <td>Medium</td>