Fix live photo identification

[OldBuddy]

Description

• fix: invalid content_type property identification for a live photo message.
• refactor: convert if blocks to match statement on content_type property.

Fixes #1841

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

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[JrooTJunior]

These changes are not related to the original problem, so they should not be changed here.

Another point is that this change reduces performance because instead of directly checking the attributes, it determines the content type and then falls back to the logic.

At the same time, when directly checking attributes, it tells type checkers that the checked attribute is not None, so it unwraps the "Optional" layer from the type, and when the attribute is passed to an API method, it clearly remains as required/passed, but when you don't check, it remains optional and is incompatible with API calls where these attributes remain required.