fix: start_time type of int instead of float
# What does this PR do ?

Fix : You can now completely use the `minimum_timestamp_duration` option, which bugged if the value was too large.

**Collection**: ASR

# Changelog 
As we could see in the traceback, the problem appeared during the use of the `get_ctm_line` function because `start_time` was a type of **int** at [this line](https://github.com/NVIDIA/NeMo/blob/main/tools/nemo_forced_aligner/utils/make_ctm_files.py#L98) :
At the beginning, `boundary_info_.t_start` is definitely a **float** with the value 0.0 and `start_time` is also a float after [copying](https://github.com/NVIDIA/NeMo/blob/main/tools/nemo_forced_aligner/utils/make_ctm_files.py#L88). Everything is fine for now.
The source of the problem is at [this line](https://github.com/NVIDIA/NeMo/blob/main/tools/nemo_forced_aligner/utils/make_ctm_files.py#L98) : When using the `max` function, if we have set a `minimum_timestamp_duration` value that is too high. `start_time` will become 0 BUT type of **int** and **no more** type of **float**.
So when we get to the use of the `get_ctm_line` function, this one checks the type of `start_time` and since it's not the right type, it raises a type exception [here](https://github.com/NVIDIA/NeMo/blob/935b9c78f4e75e873f8511121bd846e7dabca4f3/nemo/collections/asr/parts/utils/manifest_utils.py#L97).

Consequently, the **max function argument** should be changed to **0.0** to be always a type of **float**.


# Usage
- You can now really use the option **ctm_file_config.minimum_timestamp_duration=0.5** to change the value of `minimum_timestamp_duration` no matter how long the tokens/words/segments of your transcription is.
Example : 
```
python <path to NeMo>/tools/nemo_forced_aligner/align.py pretrained_name="stt_en_fastconformer_hybrid_large_pc" manifest_filepath=nemo/manifest.json output_dir=nemo/output ctm_file_config.minimum_timestamp_duration=0.5
```

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**PR Type**:
- [ ] New Feature
- [x] Bugfix
- [ ] Documentation

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# Additional Information
* Related to #8592 
