Fix issue #136: Remove dependency on speechrecognition library

[neubig]

This PR fixes issue #136 by removing the dependency on the speechrecognition library.

Changes

• Created a minimal implementation of the needed audio functionality in openhands_aci/utils/audio.py
• Updated imports in md_converter.py to use our own implementation
• Removed the speechrecognition dependency from pyproject.toml
• Added unit tests for the new audio module
• Added proper attribution for code adapted from the speech_recognition library (BSD 3-Clause License)
• Fixed linting and type checking issues

Closes #136

@neubig can click here to continue refining the PR

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • Run Python Unit Tests
  • Run Python Integration Tests

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #137

Feel free to include any additional details that might help me get this PR into a better state.

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