fix(cpp): update clangd_extensions plugin to new setup process

[mehalter]

📑 Description

clangd_extensions recently made some significant breaking changes where it doesn't actually do anything except add commands. So we can just have it load on the file types and we are good to go!

ℹ Additional Information

Extra people testing this would be super helpful!

[github-actions]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• Proper usage of opts table rather than setting things up with the config function.

[mehalter]

@Uzaaft for AstroNvim v4 we should probably just have this fully lazy loaded and then load the plugin with the clangd on_attach method! 🚀

[Uzaaft]

Shouldn't this PR add back clangd, since the plugin itself doesn't do that anymore?

[mehalter]

@Uzaaft it does that, it removes the line that skips the setup. clangd is already in the mason-lspconfig setup