ChatGPTCompleteCode does not work at all (ChatGPT does)

Hi,

I have just configured this plugin with the api_key_cmd like so:
`api_key_cmd = "op read op://somePath --no-newline",`

When I set my cursor on line 9 in the following buffer and issue ChatGPTCompleteCode
It kind of bugs out neovim. What happens is:
- ` // TODO: implement` will appear on line 9
- the closing curly brace of the message dissapears
- I can no longer undo and get the following error: `E21: Cannot make changes, 'modifiable' is off`

The code completion feature is completely unusable like this.
Any help would be greatly appreciated because what I have seen from the Dreams of Code video seems amazing.

regards,
Chris

```go
package main

import (
"flag"
"fmt"
)

func sortStringsByLength(arr []string) {
// this is line 9, in my actual test the comment is not here but the line is empty
}

func main() {
var nFlag = flag.Int("n", 1234, "help message for flag n")
flag.Parse()
fmt.Printf("nflag: %d", *nFlag)
}

```

Start by reproducing the issue with the ChatGPTCompleteCode command, the api_key_cmd configuration, and the provided Go buffer. Trace the completion flow around the inserted TODO, disappearing closing brace, and modifiable state; done means completion works without corrupting the buffer and undo remains available.

Written by the indexing model from the issue text.