docs(mariner): confirm it works with Mariner 2.0 VM

[knqyf263]

Description

Confirmed Trivy worked with CBL-Mariner 2.0 VM.

$ az group create -l ukwest -n trivy-mariner-test
$ az vm create --name mariner-test --resource-group trivy-mariner-test --image MicrosoftCBLMariner:cbl-mariner:cbl-mariner-2:latest --admin-username knqyf263 --generate-ssh-key
$ ssh knqyf263@x.x.x.x
...

knqyf263@mariner-test [ / ]$ ./trivy --cache-dir /tmp fs /
2022-04-24T16:03:53.314Z        INFO    Need to update DB
2022-04-24T16:03:53.314Z        INFO    DB Repository: ghcr.io/aquasecurity/trivy-db
2022-04-24T16:03:53.314Z        INFO    Downloading DB...
31.31 MiB / 31.31 MiB [----------------------------------------------------------------------------------------------------------------------------------] 100.00% 29.93 MiB p/s 1.3s
2022-04-24T16:04:00.869Z        INFO    Detected OS: cbl-mariner
2022-04-24T16:04:00.869Z        INFO    Detecting CBL-Mariner vulnerabilities...
2022-04-24T16:04:00.877Z        INFO    Number of language-specific files: 0

mariner-test (cbl-mariner 2.0.20220409)
=======================================
Total: 98 (UNKNOWN: 0, LOW: 4, MEDIUM: 26, HIGH: 46, CRITICAL: 22)

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).