Fix 2 paths in the doctest list
# What does this PR do?

doctest has 0 failures 
```
🌞 There were no failures: all 0 tests passed. The suite ran in 0h0m0s.
```
which is caused by 
```
ERROR: file or directory not found: src/transformers/models/maskformer/configuration_mask2former.py
collecting ... collected 0 items
```
😭😭😭
This PR makes the failures (if any) visible again.
_The documentation is not available anymore as the PR was closed or merged._