LITE-34447: Drop spurious importlib-metadata dependency

[pcaro]

Summary

importlib-metadata was declared as a direct dependency (^6.6) solely as a fallback for the stdlib importlib.metadata import in connect/client/version.py.

Since the project requires Python >=3.9 and importlib.metadata has been in the standard library since 3.8, the except branch never executed and the <7 ceiling imposed by the caret (^6.6 → >=6.6,<7) was entirely artificial.

Changes

• Remove importlib-metadata = "^6.6" from pyproject.toml.
• Remove the try/except fallback in connect/client/version.py; import directly from importlib.metadata.
• Re-lock poetry.lock.

Notes

• The library has no runtime dependency on importlib-metadata, neither direct nor transitive. It only remains in the lock at 6.11.0 as a transitive dependency of the docs toolchain (mkdocs / mkdocstrings, python_version < "3.10"), which lives in the dev-only [tool.poetry.group.docs.dependencies] group and never ships to consumers of the package.
• requirements/docs.txt is therefore unchanged: it is the Read the Docs build environment, where the mkdocs toolchain legitimately keeps pulling it in.
• The poetry.lock diff also reflects a lock-version 2.0 → 2.1 reformat from the local Poetry 2.4.1; CI installs Poetry unpinned, so it's compatible.

Verification

• pytest tests/client/test_version.py → 2 passed
• flake8 connect/client/version.py → clean

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}