Used to be able to do "percent of previous step" on funnel charts

### Describe the bug

* When you make a "funnel" chart, we used to be able to toggle between "percent of start" vs. "percent of previous step"
* Now im unable to configure this and the only option is to show "percent of start"
* Can we add this configuration back in?

### To Reproduce

* Create some steps
* Select funnel visualisation
* Click around and cannot change visualisation to "percent of previous step"

### Expected behavior

_No response_

### Logs

_No response_

### Information about your Metabase installation

```JSON
{
"browser-info": {
"language": "en-US",
"platform": "MacIntel",
"userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36",
"vendor": "Google Inc."
},
"system-info": {
"file.encoding": "UTF-8",
"java.runtime.name": "OpenJDK Runtime Environment",
"java.runtime.version": "11.0.22+7",
"java.vendor": "Eclipse Adoptium",
"java.vendor.url": "https://adoptium.net/",
"java.version": "11.0.22",
"java.vm.name": "OpenJDK 64-Bit Server VM",
"java.vm.version": "11.0.22+7",
"os.name": "Linux",
"os.version": "5.10.209-198.858.amzn2.x86_64",
"user.language": "en",
"user.timezone": "GMT"
},
"metabase-info": {
"databases": [
"postgres",
"snowflake",
"redshift"
],
"hosting-env": "unknown",
"application-database": "postgres",
"application-database-details": {
"database": {
"name": "PostgreSQL",
"version": "14.7"
},
"jdbc-driver": {
"name": "PostgreSQL JDBC Driver",
"version": "42.6.0"
}
},
"run-mode": "prod",
"version": {
"date": "2024-03-04",
"tag": "v0.48.8",
"hash": "a900c85"
},
"settings": {
"report-timezone": null
}
}
}
```

### Severity

Annoying, blocking interpretation and insights on which step is the biggest drop off

### Additional context

_No response_

Reproduce the issue by creating funnel-chart steps and checking whether the visualization can switch between “percent of start” and “percent of previous step.” Trace the funnel-chart configuration from that interaction; done means the “percent of previous step” option is available and correctly shows each step relative to the preceding step.

Written by the indexing model from the issue text.