docs(python): add note to using pip freeze for compatible releases

[DmitriyLewen]

Description

See #5743 (reply in thread)

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)
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[knqyf263]

We should mention Trivy parses == [exact version] only. All other specifiers are ignored, like >=, ~=, < and == 1.2.*.
https://pip.pypa.io/en/stable/reference/requirement-specifiers/

[DmitriyLewen]

Good point!
I updated docs.