Plot is duplicated with repeated calls to plt.show()

Nobody has claimed this yet.

## Describe the issue
When I use the "%matplotlib ipympl" backend and display a plot with plt.show(), it works fine, but that plot is displayed again for every future call to plt.show(). The expected behavior is for show() to not repeat the plot output. This occurs with a fresh Anaconda (2024.10-1) installation of Python (3.12.7). This does not happen with default backend.

## Versions

```
3.12.7 | packaged by Anaconda, Inc. | (main, Oct 4 2024, 08:22:19) [Clang 14.0.6 ]
ipympl version: 0.9.6
Selected Jupyter core packages...
IPython : 8.30.0
ipykernel : 6.29.5
ipywidgets : 8.1.5
jupyter_client : 8.6.0
jupyter_core : 5.7.2
jupyter_server : 2.14.1
jupyterlab : 4.2.5
nbclient : 0.8.0
nbconvert : 7.16.4
nbformat : 5.10.4
notebook : 7.2.2
qtconsole : 5.6.0
traitlets : 5.14.3
usage: jupyter [-h] [--version] [--config-dir] [--data-dir] [--runtime-dir]
[--paths] [--json] [--debug]
[subcommand]

Jupyter: Interactive Computing

positional arguments:
subcommand the subcommand to launch

options:
-h, --help show this help message and exit
--version show the versions of core jupyter packages and exit
--config-dir show Jupyter config dir
--data-dir show Jupyter data dir
--runtime-dir show Jupyter runtime dir
--paths show all Jupyter paths. Add --json for machine-readable
format.
--json output paths as machine-readable json
--debug output debug information about paths

Available subcommands: console dejavu events execute kernel kernelspec lab
labextension labhub migrate nbconvert notebook qtconsole run server
troubleshoot trust

Jupyter command `jupyter-nbextension` not found.
```
I believe that last error is expected for notebook>7, but I'm not certain.

The issue names no source files or tests. First reproduce the repeated plt.show() behavior with the %matplotlib ipympl backend on the reported Jupyter and Python versions, then compare it with the default backend. Done means repeated show() calls no longer duplicate the existing plot output.

Written by the indexing model from the issue text.