function in VAD utils hardcoded to only use `.wav` files
**Describe the bug**

[This line](https://github.com/NVIDIA/NeMo/blob/372f519ddba0c57272d190d83eaa3169ff6f3488/nemo/collections/asr/parts/utils/vad_utils.py#L1077) uses only `.wav` to split filepaths to create filenames. However if the files are not `.wav`, this will still run, but with wrong file names which causes later on in the [`vad_infer.py` ](https://github.com/NVIDIA/NeMo/blob/c1abc047d1d5962019f7789b20d8092c7e55b690/examples/asr/speech_classification/vad_infer.py#L4) file to not fine the current files at the last stage where we create the final manifest. Specifically, in [here](https://github.com/NVIDIA/NeMo/blob/c1abc047d1d5962019f7789b20d8092c7e55b690/examples/asr/speech_classification/vad_infer.py#L163), if the file was `.flac`, we will be looking for `utt.txt` whereas the actual file created by the previous steps will be named `utt.flac.txt`.

**Steps/Code to reproduce bug**

- Use non wav files as data.
- run vad_infer.py

**Expected behavior**

It should handle different file formats.

**Environment overview (please complete the following information)**

N/A

**Environment details**

N/A

**Additional context**

N/A
