chore: drop unused vendor deps from four extensions

[leepokai]

Four extensions declare a third-party dependency they never use. This removes
those declarations from both requirements.txt and pyproject.toml.

Extension	Removed	Why
gladia_asr_python	deepgram-sdk==3.9.0	A Gladia extension depending on Deepgram's SDK. No reference to deepgram anywhere in the directory, tests included. It also pulls in httpx, aiohttp, aiofiles, dataclasses-json, aenum, deprecation and typing-extensions for nothing.
azure_mllm_python	pydub==0.25.1	Declared, never imported.
openai_mllm_python	pydub==0.25.1	Declared, never imported.
stepfun_mllm_python	pydub==0.25.1	Declared, never imported.

glm_mllm_python is deliberately left untouched — it is the one MLLM extension
that genuinely uses pydub (extension.py:16, from pydub import AudioSegment).
That contrast is what makes the removal criterion safe rather than a blanket sweep.

This follows the same direction as #2207, which scoped numpy to the extensions
that actually need it.

Verification

• Searched every file type in each of the four extension directories, tests
  included. The only occurrences of the removed packages were the dependency
  declarations themselves.
• Ran an AST pass over every .py file in the four extensions to list
  third-party imports and check each against the remaining declared deps. This
  is the check that matters for a dependency removal, since an import can be
  satisfied only transitively by the package being dropped.
• That pass flagged one case: gladia_asr_python imports typing_extensions
  without declaring it, and deepgram-sdk had required typing-extensions>=4.9.0.
  It resolves safely — the import is in tests/conftest.py only, and pydantic
  (still declared) requires typing-extensions>=4.14.1.
• Installed the post-removal requirements.txt in a clean venv for
  gladia_asr_python and for azure_mllm_python, then executed the imports the
  code actually performs. from typing_extensions import override resolves
  (4.16.0, via pydantic); aiohttp and pydantic resolve. deepgram, httpx
  and pydub are absent, confirming the slimming takes effect.
  openai_mllm_python and stepfun_mllm_python have a post-removal
  requirements.txt identical to azure_mllm_python, so that run covers all three.

Not verified

The repository test suite was not run — task test-extension needs the
ten_agent_dev container and Docker was unavailable on this machine. No Python
source is touched by this change; it removes four unused dependency
declarations only. Opening as a draft so the extension tests can run in CI
before this is considered ready.