[BUG] `vim.F.if_nil()` is deprecated in Neovim `>=v0.13`

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Current Behavior

I'm using Neovim nightly. When using this plugin, running `:checkhealth vim.deprecated`, I get a deprecation warning related to `vim.F.if_nil()`, [which is being deprecated](https://neovim.io/doc/user/deprecated/#deprecated-0.13) for Neovim `>=v0.13`.

### Expected Behavior

No deprecation warnings.

### Steps To Reproduce

1. Open Neovim Nightly
2. Use Toggleterm
3. Run `:checkhealth vim.deprecated`

### Environment

```Markdown
- OS: Arch Linux
- neovim version: v0.13.0-dev-923+g8dfe4d6629
- Shell: bash
```

### Anything else?

Demonstration: