Add reminder to free RID's in compute shader tutorial

[DevPoodle]

Closes #8447.

I've added a little section at the end of the compute shader tutorial to remind the reader to free RID's when they're finished using them. I also went through and removed some static type hints from the code blocks on this page to make it more consistent with the rest of the manual.

[thibault]

Hi. I stumbled upon this PR while searching about this topic. While this addition is very useful, I feel it would be interesting to add more details about the reason it is necessary to clear rids. Like, you have to clear rids, but why? Does the entire resource stays in memory forever? Or is there a limited amount of available rids?

[thibault]

Another comment : On the water_plane demo on godot-demo-projects, you can find this comment related to rid freeing code:

Note that our sets and pipeline are cleaned up automatically as they are dependencies :P

I find that rather confusing, so it seems there's a little more to it than just clearing every single created RID? (sorry if it outside the current PR initial scope).

[DevPoodle]

@thibault Clearing RID's is important because by default their memory isn't cleared when they go out of scope, meaning you can very easily cause a memory leak when using them. As for the types of RID's that are cleared automatically, if you free the shader first, then I believe it also frees the pipeline and uniform sets. I think that would be better documented under the create_shader and free_rid methods than here though.

Edit: There's already a PR for it: #103113

[skyace65]

Thanks! And congrats on your first merged PR!