docs(repo): Update trivy repo usage and example

[fbufler]

Description

This PR adjusts the usage of the trivy repo command to mirror the changes regarding the support of "local repositories".
As this is my first PR, please tell me if I missed something!

Before

trivy repository --help

Scan a remote repository

Usage:
  trivy repository [flags] REPO_URL

Aliases:
  repository, repo

Examples:
  # Scan your remote git repository
  $ trivy repo https://github.com/knqyf263/trivy-ci-test
...

After

trivy repository --help

Scan a repository

Usage:
  trivy repository [flags] (REPO_PATH | REPO_URL)

Aliases:
  repository, repo

Examples:
  # Scan your remote git repository
  $ trivy repo https://github.com/knqyf263/trivy-ci-test
  # Scan your local git repository
  $ trivy repo /path/to/your/repository
...

Related issues

• Close doc: update trivy repo usage and example #4985

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. -> Just documentation changes
• 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).

[CLAassistant]

All committers have signed the CLA.

[CLAassistant]

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[knqyf263]

Perfect. Thanks!