Clarify documentation on --max_idle_secs=0

"This option specifies how long, in seconds, the Blaze server process should wait before it exits.  To disable the feature" is ambiguous in what the "feature" is.  I thought the "wait" was the feature, but apparently it was the "exit".

RELNOTES: N/A
PiperOrigin-RevId: 265043526

site/docs/user-manual.html

diff --git a/site/docs/user-manual.html b/site/docs/user-manual.html
index 30f6044..cddc5b6 100644
--- a/site/docs/user-manual.html
+++ b/site/docs/user-manual.html
@@ -2835,7 +2835,8 @@
 <p>
   This option specifies how long, in seconds, the Bazel server process
   should wait after the last client request, before it exits.  The
-  default value is 10800 (3 hours). To disable the feature, set `--max_idle_secs=0`.
+  default value is 10800 (3 hours). <code class='flag'>--max_idle_secs=0</code> will cause the
+  Bazel server process to persist indefinitely.
 </p>
 <p>
   This option may be used by scripts that invoke Bazel to ensure that