Auto-switch the input dimensions in the conformer encoder adapter to correct value
Signed-off-by: Shantanu Acharya <shantanua@nvidia.com>

# What does this PR do ?

Fixed the issue where the auto-switching functionality of the `ConformerEncoderAdapter` input feature dimension was missing.

**Collection**: ASR

# Changelog 

File changed: `nemo/collections/asr/modules/conformer_encoder.py`

Function added: `_update_adapter_cfg_input_dim`
Updates the `in_features` value in the adapter config with the correct value i.e. `self.d_model`

Function modified: `add_adapter`
Calls the `self._update_adapter_cfg_input_dim` function to update the adapter input feature dimensions.

# Before your PR is "Ready for review"
**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [ ] New Feature
- [x] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in NeMo ASR.
