Ubuntu 21.10 reaches end of life on Jul 14, 2022

[rbhanda]

Ubuntu 21.10 reaches end of life on July 14, 2022 This issue is created to track progress for the remove support for Ubuntu 21.10 from .NET Core 3.1 and .NET 6.0

Repos team to update:

• [ ] Remove installers for the outdated distro
• [ ] Remove build support
• [ ] Remove test assets

Infrastructure Team Accountabilities/Deliverables:

• [ ] Notification to NetCore Engineering Partners
• [ ] Remove the outdated version from the hardware pool

Release Team

• [x] Send Notification to every team in .NET for upcoming addition
• [ ] Supported OS content gets updated on GitHub and marketing sites.
• [ ] Update release manifest files.
• [ ] Docker files which are used for install testing needs to be updated.

Document updates:

• [ ] Add/Remove OS prerequisites to the dependencies document
• [ ] Update distro install page

[adegeo]

Created dotnet/docs#30110 for docs