fix(ubuntu): update eol dates for Ubuntu

[afdesk]

Description

Ubuntu's List of releases contains two breaking dates: End of Standard Support and End of Life.
Now Trivy depends on End of Life for LTS versions, but we should use "EOL" here in a general sense, so this PR sets eolDates from End of Standard Support for LTS and End of Life for ESM.

before:

$ trivy image ubuntu:16.04
2023-05-10T13:41:18.648+0600	INFO	Secret scanning is enabled
2023-05-10T13:41:18.648+0600	INFO	If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2023-05-10T13:41:18.648+0600	INFO	Please see also https://aquasecurity.github.io/trivy/dev/docs/secret/scanning/#recommendation for faster secret detection
2023-05-10T13:41:30.911+0600	INFO	Detected OS: ubuntu
2023-05-10T13:41:30.911+0600	INFO	Detecting Ubuntu vulnerabilities...
2023-05-10T13:41:30.912+0600	INFO	Number of language-specific files: 0

ubuntu:16.04 (ubuntu 16.04)

Total: 0 (UNKNOWN: 0, LOW: 0, MEDIUM: 0, HIGH: 0, CRITICAL: 0)

after:

$ trivy image ubuntu:16.04
2023-05-10T14:04:35.747+0600	INFO	Secret scanning is enabled
2023-05-10T14:04:35.747+0600	INFO	If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2023-05-10T14:04:35.747+0600	INFO	Please see also https://aquasecurity.github.io/trivy/dev/docs/secret/scanning/#recommendation for faster secret detection
2023-05-10T14:04:48.002+0600	INFO	Detected OS: ubuntu
2023-05-10T14:04:48.002+0600	INFO	Detecting Ubuntu vulnerabilities...
2023-05-10T14:04:48.003+0600	INFO	Number of language-specific files: 0
2023-05-10T14:04:48.003+0600	WARN	This OS version is no longer supported by the distribution: ubuntu 16.04
2023-05-10T14:04:48.003+0600	WARN	The vulnerability detection may be insufficient because security updates are not provided

ubuntu:16.04 (ubuntu 16.04)

Total: 0 (UNKNOWN: 0, LOW: 0, MEDIUM: 0, HIGH: 0, CRITICAL: 0)

I added the screenshots for history

Related issues

• Close Ubuntu 16.04 LTS vulns not reported #3701

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).