(🐞) `--update-data` removes escapes

```py
[case testSomethingSus]
\[1] + 1
```
```
> pytest mypy --update-data
```
# Expected
```py
[case testSomethingSus]
\[1] + 1  # E: Something sus  [sus]
```
# Actual
```py
[case testSomethingSus]
[1] + 1  # E: Something sus  [sus]
```