Documentation: guides: pipeline-handler: Update clamp() namespace

Update the sample code using utils::clamp() to std::clamp().

Fixes: f2734ff3ab ("libcamera: Replace utils::clamp() with std::clamp()")
Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Documentation/guides/pipeline-handler.rst

@@ -1289,7 +1289,7 @@ range definitions and their corresponding values on the device before being set.
                  }
 
                  int32_t value = lroundf(it.second.get<float>() * 128 + offset);
-                 controls.set(cid, utils::clamp(value, 0, 255));
+                 controls.set(cid, std::clamp(value, 0, 255));
           }
 
           for (const auto &ctrl : controls)