Fix issue with thumbnail in InputMedia types

[hecklawert]

Description

• Fixed an issue where InputFile objects in the thumbnail field caused JSON serialization errors.

• Modified the function convert_input_media_array to extract InputFile objects from thumbnail and replace them with attach:// references.

Describe your tests

• Tested with multiple configurations of InputMedia arrays, including videos and images with local files as thumbnail.

• Verified successful requests to the Telegram API to upload media groups with proper file attachments.

• Confirmed that JSON serialization no longer fails when InputFile is present.

Python version:
3.12

OS:
Debian 12

Checklist:

• I added/edited example on new feature/change (if exists)
• My changes won't break backward compatibility
• I made changes both for sync and async

Related to #2429

[Badiboy]

I have nothing against this PR, but cannot confirm if it is right or not.
@coder2020official May be you can?

[coder2020official]

Hi, sorry took me a while to write this comment. This change looks reasonable, however, you haven't made changes for the async version. Could you do that as well?

[hecklawert]

@coder2020official Hi, sorry. I thought the changes made were also intended for the asynchronous version. I have made the corrections, but please be aware that I am currently unable to test with the asynchronous version.

[Badiboy]

Looks fine. Thank you.