Jenkins script "install-plugins.sh" fails due to missing plugins

Issue

• When using the registry.redhat.io/openshift4/ose-jenkins:v4.10 image and running the /usr/local/bin/install-plugins.sh command, it fails with a "Plugin not found" error:

  STEP 3/3: RUN /usr/local/bin/install-plugins.sh /opt/openshift/my-plugins.txt
  [..]
  Downloading plugins...
  [..]
  Installed plugins:
  [..]
  Verifying Locked Plugins in Bundle...
  Missing nexus-jenkins
  Missing slack
  Missing ssh-agent
  
  Some errors were encountered!
  Plugin nexus-jenkins not found in /opt/openshift/plugins/bundle-plugins.txt
  Plugin slack not found in /opt/openshift/plugins/bundle-plugins.txt
  Plugin ssh-agent not found in /opt/openshift/plugins/bundle-plugins.txt
  Error: building at STEP "RUN /usr/local/bin/install-plugins.sh /opt/openshift/my-plugins.txt": while running runtime: exit status 1