I have a large document with a similar structure:

```
Data800,
Data900,
Data1000,
]
}

```

How would I go about removing the last character from the 3rd to last line (in this case, where the comma is positioned next to Data1000). The output should look like this:

```
Data800,
Data900,
Data1000
]
}

```

It will always be the 3rd to last line in which needs the last character removed. Back-end is linux, and can use perl, bash, python, etc.