[BUG] Lines send before REPL is opened

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When I send line to terminal, with whatever command, for example with
```
require("toggleterm").send_lines_to_terminal("single_line", trim_spaces, { args = vim.v.count })
```
the line is send a first time before the REPL is opened, and a second time after it has been opened.

Here is a video:
[20240301T132234.webm](https://github.com/akinsho/toggleterm.nvim/assets/54762742/d84dabb4-3fd6-4cdd-be93-2bdc8dd5c69d)

### Expected Behavior

The line should be send only one time after the REPL has opened.

### Steps To Reproduce

1. Open a file
2. Send line to terminal

### Environment

```Markdown
- OS: Arch Linux
- neovim version: 0.9.5
- Shell: bash
```

### Anything else?

_No response_