fix(config): add Ubuntu 20.10

[shigechika]

If this Pull Request is work in progress, Add a prefix of “[WIP]” in the title.

What did you implement:

add to support Ubuntu 20.10

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

% make test
    --- PASS: TestEOL_IsStandardSupportEnded/Ubuntu_20.10_supported (0.00s)

% vuls report
example (ubuntu20.10)
=========================================
Total: 0 (Critical:0 High:0 Medium:0 Low:0 ?:0)
0/0 Fixed, 0 poc, 0 exploits, en: 0, ja: 0 alerts
776 installed

Warning: Some warnings occurred.
[Standard OS support will be end in 3 months. EOL date: 2021-07-01]


No CVE-IDs are found in updatable packages.
776 installed

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: NO

Reference

• https://blog.github.com/2015-01-21-how-to-write-the-perfect-pull-request/