Avoid chunking abbreviations

### Bug description

Extra chunking could occur on words like Mr. and Dr.

See test `fs2.tests.test_cli.PrepareSynthesizeDataTest`

### How to reproduce the bug

```python
# Sample code to reproduce the problem
```

### Error messages and logs

```
# Error messages and logs here please
```

### Environment

Current environment

# Please paste the output of `everyvoice --diagnostic` here

# EveryVoice Diagnostic information

### More info

_No response_

Start by reading and running fs2.tests.test_cli.PrepareSynthesizeDataTest, which the issue identifies as covering the problem. Trace the chunking behavior for abbreviations such as Mr. and Dr.; done means those words no longer receive extra chunking and the relevant test passes.

Written by the indexing model from the issue text.