CI for Security/CloudFoundrySingleSignon 2.x failing due to Ruby version

[ccheetham]

Newer VM images no longer include Ruby 2.4 used by UAA client:

2021-02-24T14:30:12.5410618Z ##[section]Starting: Setup Ruby
2021-02-24T14:30:12.5417268Z ==============================================================================
2021-02-24T14:30:12.5417888Z Task         : Use Ruby version
2021-02-24T14:30:12.5418384Z Description  : Use the specified version of Ruby from the tool cache, optionally adding it to the PATH
2021-02-24T14:30:12.5418972Z Version      : 0.182.0
2021-02-24T14:30:12.5419359Z Author       : Microsoft Corporation
2021-02-24T14:30:12.5419881Z Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/tool/use-ruby-version
2021-02-24T14:30:12.5420450Z ==============================================================================
2021-02-24T14:30:12.7983914Z ##[error]Version spec 2.4.x for architecture %25s did not match any version in Agent.ToolsDirectory.
Available versions: /opt/hostedtoolcache
2.5.8,2.6.6,2.7.2,3.0.0
If this is a Microsoft-hosted agent, check that this image supports side-by-side versions of Ruby at https://aka.ms/hosted-agent-software.
If this is a self-hosted agent, see how to configure side-by-side Ruby versions at https://go.microsoft.com/fwlink/?linkid=2005989.
2021-02-24T14:30:12.8019640Z ##[section]Finishing: Setup Ruby