Unable to download ssh-agent plugin via plugin manager

We are trying to download and install ssh-agent through plugin manager by specifying the plugin Id as and the version as <1.20> it is unable to install but other plugins gets installed.
Please let us know what I am missing.
CLI version: 2.5.0

content on plugins.yaml
```yaml
plugins:
- artifactId: git
source:
version: latest
- artifactId: configuration-as-code
source:
version: latest
- artifactId: groovy
source:
version: latest
- artifactId: job-dsl
source:
version: latest
- artifactId: active-directory
source:
version: latest
- artifactId: ssh-agent
source:
version: 1.20
- artifactId: ssh
```

Start with the plugins.yaml configuration and reproduce the ssh-agent 1.20 installation using CLI version 2.5.0, comparing it with the other listed plugins. Done means identifying why this entry fails and confirming a correction or clearly documented limitation.

Written by the indexing model from the issue text.