Update to resolve Issue with outdated _convert_entities function in copy_message method

[YouKnow-sys]

Description

I identified an issue with the outdated function _convert_entities used in both the sync and async versions of the copy_message method. This function was not functioning correctly, resulting in invalid entities. While all other methods were using a more updated method for converting entities, this particular method was still relying on _convert_entities.

To address this issue, I have removed _convert_entities and replaced it with more better json.dumps(types.MessageEntity.to_list_of_dicts(...)). This change ensures that the entities are properly converted and are valid

Python version:
3.12

OS:
windows 10

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

[Badiboy]

Looks reasonable, thank you.

[Badiboy]

Could you please enchance MessageEntity.to_list_of_dicts with _convert_entities checks?

1. None or empty => None
2. If not serializable => entities
3. Else - make list.

[YouKnow-sys]

Could you please enchance MessageEntity.to_list_of_dicts with _convert_entities checks?

1. None or empty => None
2. If not serializable => entities
3. Else - make list.

Ok so I updated the MessageEntity.to_list_of_dicts with a few changes, instead of checking if the object is instance of JsonSerializable I check if they are instance of MessageEntity, because this is more accurate.
although checking the instance for just the first element isn't that accurate, user can still pass other types in the list, but I didn't want to sacrifice more performance to check every element...

[Badiboy]

LGTM. Thank you.