Restore relaxation of openai version range, lost after refactor

[srowen]

Recently, #8075 was opened to note that limiting openai to version 1.61.0 was causing problems.

This was fixed for 2.6.18 in #8084 . However that change only changed one of two entries in pyproject.toml that defines the openai range, as there were parallel configurations of dependencies for poetry and uv.

Then, just before 2.6.19, this PR removed the poetry-oriented dependencies, including the openai change:
0363c2e#diff-50c86b7ed8ac2cf95bd48334961bf0530cdc77b5a56f852c5c61b89d735fd711L36-L106

Now, pyproject.toml is left with the other copy which still has the version limit of 1.61.0:
https://github.com/stanfordnlp/dspy/blob/main/pyproject.toml#L27

This just completes the intent of the original change by removing the version limit on openai.

CC @okhat @chenmoneygithub

[okhat]

Ah, thanks so much @srowen !