Some bundled plugins are ignored and not updated

Current Jenkins LTS version is 2.263.3. This version has a bouncycastle-api plugin bundled, version 2.16. However, latest version is 2.18. The Jenkins UI reveals this:

However, running plugin manager 2.5.0 (latest) doesn't update it:
```
$ cd /tmp

$ curl -OLs https://get.jenkins.io/war-stable/2.263.3/jenkins.war

$ curl -OLs https://github.com/jenkinsci/plugin-installation-manager-tool/releases/download/2.5.0/jenkins-plugin-manager-2.5.0.jar

$ java -jar jenkins-plugin-manager-2.5.0.jar --war jenkins.war --list | grep bouncy # no ouput here

$ java -jar jenkins-plugin-manager-2.5.0.jar --war jenkins.war --available-updates
No available updates
```

Same happens with the `command-launcher` and `jdk-tool` plugins, both bundled in the latest LTS.

Later edit note: adding the plugin explicitly to the command line `i.e. via --plugins bouncecastle-api` will find the latest 2.18 version and download it. But the problem is that it doesn't detect the bundled version.