plugin.xml <dependency> tag commit attribute doesn't work as documented for branches

# Bug Report

## Problem

The documentation on how to use plugin.xml dependency tag does not match usage.
Either there is a bug in cordova-lib or the documentation is incorrect.

Here is the documentation:

### What is expected to happen?
When installing a plugin that has this dependency tag in plugin.xml:
```xml

```
I expect that most recent version on branch `2.x-custom` should be retrieved.

### What does actually happen?

Instead it seems to ignore the `commit` attribute and fetches the `master` branch. Here is the log:

```
Plugin dependency "cordova-plugin-ionic-webview" not fetched, retrieving then installing.
fetch: Installing https://github.com/miloproductionsinc/cordova-plugin-ionic-webview.git to S:\Projects\MiloProductions\hello
Running command: npm install https://github.com/miloproductionsinc/cordova-plugin-ionic-webview.git --production --save
```

## Information

Interestingly, this *does* produce the desired result:
```

```

### Environment, Platform, Device

windows building android
mac building ios

### Version information

cordova 9.0.0
cordova-lib 9.0.1

Any plugin with this type of dependancy should demonstrate this problem, but in this case, my examples are retrieving:

## Checklist

- [x] I searched for existing GitHub issues
- [x] I updated all Cordova tooling to most recent version
- [x] I included all the necessary information above