docs: split commands to download db for different versions of oras

[DmitriyLewen]

Description

In oras v0.13.0 the -a/--allow-all behavior is set by default and these flags have been removed(oras-project/oras#387).
Also grouping code blocks was used:
e.g.:

Related issues

• Close Offline use documentation includes obsolete flag to oras #2580

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).

[knqyf263]

Can we use "grouping code blocks"?
https://squidfunk.github.io/mkdocs-material/reference/content-tabs/#linked-content-tabs

Suggested change

	```
	$ oras pull ghcr.io/aquasecurity/trivy-db:2
	```
	for `oras` v0.12.0 or earlier, `-a` flag must be used:
	=== oras >= v0.13.0
	```
	$ oras pull ghcr.io/aquasecurity/trivy-db:2
	```
	=== oras < v0.13.0
	```
	$ oras pull -a ghcr.io/aquasecurity/trivy-db:2
	```

[DmitriyLewen]

Done.