Duplicate raylines when changing topic in `Visualize frustum` plugin

## Environment
* OS Version: Ubuntu 24.04
* Source or binary build?
source , gz-rendering10
* If this is a GUI or sensor rendering bug, describe your GPU and rendering system. Otherwise delete this section.
- Rendering plugin: ogre2

## Description
* Expected behavior: only raylines of selected topic
* Actual behavior: duplicate raylines

## Steps to reproduce

1. gz sim visualize_frustum_rgb_camera.sdf
2. refresh and change topic in visualize frustum GUI plugin

the screenshot from the [Extend rgb camera for visualize frustum plugin#3374](https://github.com/gazebosim/gz-sim/pull/3374)

Run `gz sim visualize_frustum_rgb_camera.sdf`, then use the Visualize frustum GUI plugin to refresh and change the topic. Trace the plugin's rayline handling across a topic change and compare the rendered result with the selected topic. Done means only raylines for the selected topic remain, without duplicates.

Written by the indexing model from the issue text.