Electrophysiology viewer plugin not shown in the Sandbox

**Describe the bug**

Following the [tutorial](https://bluebrainnexus.io/docs/getting-started/try-nexus.html) I uploaded some datasets to the sandbox.
However, when clicking on the first trace and then on the `Electrophysiological Recording Viewer` plugin the rendering does not seem to work

**What part of Nexus is affected**
- [x] Fusion
- [ ] Delta
- [ ] CLI
- [ ] Documentation

**To Reproduce**
Steps to reproduce the behavior, e.g. for Fusion:
1. Select a "Trace" "Dataset"
2. Click on 'Electrophysiological Recording Viewer'

**Expected behavior**

I expect to see traces

**Screenshots**

**Additional context**
sandbox and staging environment

**Implementation**
- create a config map with the manifest.json file that excludes the plugin
- mount the config map over the default config map of the image
- add comment to the image version
- add internal docs to explain how this works