fix : use the earlier name of the player input script

[a2937]

Renames the class Sprite back to MySprite2D in the player input lesson plan.

Closes #8417

[skyace65]

A more comprehensive fix needs to be done for this issue. the C# name doesn't match the GDScript name, and the GDScript name doesn't match the image for creating the script, and instructions should be given to give it a specific name. Also having people just add a underscore to make the script name not the node name is probably bad practice.

Would you like to update this PR to do those changes? If not I can make a separate PR fixing them.

[a2937]

Oh my. You're right. I'll see what I can do. But I would like some clarifications.

1. What should the GD script name be?
2. What should the C# class name be?
3. Will we need to make any new images for the guide?

[Piralein]

The script name should be snake_case: sprite_2d.gd, please note our image format guidelines, the image should be in .webp format.
The image file in question

I believe the c# name change is correct, as it is already named like this in the previous guide setting up the script.

[a2937]

How did I do Piralein?
I am aware I need to crop it some more, but I wanna make sure the necessary information is there.

[Piralein]

@a2937 The template needs to be set to Object: Empty, as instructed in the step by step guide.

Adding the yellow outline for the "Template" input would be great. (it isn't necessary for the path)
The color definition can be found in the image guideline (fffb44 with like 2px width)

[skyace65]

This PR is good now that Piralein updated the image in #8558

[skyace65]

Thanks!

[mhilbrunner]

Cherry-picked to 4.2.